Fix the total amount the user owes/is owed for optimised debts

[IsaacCheng9]

Bug Report

• When turning on 'Smart Split', the total amount the user owes/is owed isn't always updated correctly.
• This is likely caused by a missing await on when clearing the optimised debt model collection here.
• However, adding an await statement causes test failures:

isaac@MBP16 server % npm test

> server@1.0.0 test
> jest --verbose --coverage

 PASS  routes/users.test.js
  Test for user routes
    ✓ GET /users (24 ms)
    ✓ POST /users (18 ms)
    ✓ GET /users/:username (6 ms)
    ✓ DELETE /users/:username (4 ms)

 PASS  routes/expenses.test.js
  Test for expense routes
    ✓ GET /expenses (20 ms)
    ✓ POST /expenses (24 ms)
    ✓ POST /expenses/settlement (6 ms)

/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/lib/operations/execute_operation.js:20
                return callback(new error_1.MongoNotConnectedError('Client must be connected before running operations'));
                                ^

MongoNotConnectedError: Client must be connected before running operations
    at /Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/operations/execute_operation.ts:89:11
    at maybePromise (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/utils.ts:518:3)
    at executeOperation (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/operations/execute_operation.ts:83:22)
    at Collection.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/collection.ts:624:28)
    at NativeCollection.<computed> [as deleteMany] (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/drivers/node-mongodb-native/collection.js:202:33)
    at NodeCollection.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mquery/lib/collection/node.js:90:21)
    at model.Query.Object.<anonymous>.Query.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mquery/lib/mquery.js:2661:20)
    at model.Query.<anonymous> (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/query.js:3211:32)
    at model.Query._wrappedThunk [as _deleteMany] (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/helpers/query/wrapThunk.js:27:8)
    at /Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/kareem/index.js:426:25 {
  [Symbol(errorLabels)]: Set(0) {}
}

Node.js v18.2.0
/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/lib/operations/execute_operation.js:20
                return callback(new error_1.MongoNotConnectedError('Client must be connected before running operations'));
                                ^

MongoNotConnectedError: Client must be connected before running operations
    at /Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/operations/execute_operation.ts:89:11
    at maybePromise (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/utils.ts:518:3)
    at executeOperation (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/operations/execute_operation.ts:83:22)
    at Collection.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/collection.ts:624:28)
    at NativeCollection.<computed> [as deleteMany] (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/drivers/node-mongodb-native/collection.js:202:33)
    at NodeCollection.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mquery/lib/collection/node.js:90:21)
    at model.Query.Object.<anonymous>.Query.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mquery/lib/mquery.js:2661:20)
    at model.Query.<anonymous> (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/query.js:3211:32)
    at model.Query._wrappedThunk [as _deleteMany] (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/helpers/query/wrapThunk.js:27:8)
    at /Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/kareem/index.js:426:25 {
  [Symbol(errorLabels)]: Set(0) {}
}

Node.js v18.2.0
/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/lib/operations/execute_operation.js:20
                return callback(new error_1.MongoNotConnectedError('Client must be connected before running operations'));
                                ^

MongoNotConnectedError: Client must be connected before running operations
    at /Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/operations/execute_operation.ts:89:11
    at maybePromise (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/utils.ts:518:3)
    at executeOperation (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/operations/execute_operation.ts:83:22)
    at Collection.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/collection.ts:624:28)
    at NativeCollection.<computed> [as deleteMany] (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/drivers/node-mongodb-native/collection.js:202:33)
    at NodeCollection.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mquery/lib/collection/node.js:90:21)
    at model.Query.Object.<anonymous>.Query.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mquery/lib/mquery.js:2661:20)
    at model.Query.<anonymous> (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/query.js:3211:32)
    at model.Query._wrappedThunk [as _deleteMany] (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/helpers/query/wrapThunk.js:27:8)
    at /Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/kareem/index.js:426:25 {
  [Symbol(errorLabels)]: Set(0) {}
}

Node.js v18.2.0
/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/lib/operations/execute_operation.js:20
                return callback(new error_1.MongoNotConnectedError('Client must be connected before running operations'));
                                ^

MongoNotConnectedError: Client must be connected before running operations
    at /Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/operations/execute_operation.ts:89:11
    at maybePromise (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/utils.ts:518:3)
    at executeOperation (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/operations/execute_operation.ts:83:22)
    at Collection.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongodb/src/collection.ts:624:28)
    at NativeCollection.<computed> [as deleteMany] (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/drivers/node-mongodb-native/collection.js:202:33)
    at NodeCollection.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mquery/lib/collection/node.js:90:21)
    at model.Query.Object.<anonymous>.Query.deleteMany (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mquery/lib/mquery.js:2661:20)
    at model.Query.<anonymous> (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/query.js:3211:32)
    at model.Query._wrappedThunk [as _deleteMany] (/Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/mongoose/lib/helpers/query/wrapThunk.js:27:8)
    at /Users/isaac/Library/CloudStorage/OneDrive-Personal/Documents/Programming/Projects/fairsplit/server/node_modules/kareem/index.js:426:25 {
  [Symbol(errorLabels)]: Set(0) {}
}

Node.js v18.2.0
 FAIL  routes/debts.test.js
  ● Test suite failed to run

    Jest worker encountered 4 child process exceptions, exceeding retry limit

      at ChildProcessWorker.initialize (node_modules/jest-worker/build/workers/ChildProcessWorker.js:211:21)

------------------------|---------|----------|---------|---------|-------------------------------------------
File                    | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s                         
------------------------|---------|----------|---------|---------|-------------------------------------------
All files               |   79.27 |    34.61 |   81.81 |   79.27 |                                           
 controllers            |   94.73 |       50 |     100 |   94.73 |                                           
  expense_controller.js |    91.3 |       50 |     100 |    91.3 | 10,18                                     
  user_controller.js    |     100 |      100 |     100 |     100 |                                           
 controllers/helpers    |   51.16 |    31.81 |      50 |   51.16 |                                           
  index.js              |   51.16 |    31.81 |      50 |   51.16 | ...9,43-44,53,65-74,93,96,101-107,119-138 
 models                 |     100 |      100 |     100 |     100 |                                           
  debt.js               |     100 |      100 |     100 |     100 |                                           
  expense.js            |     100 |      100 |     100 |     100 |                                           
  optimised_debt.js     |     100 |      100 |     100 |     100 |                                           
  user.js               |     100 |      100 |     100 |     100 |                                           
  user_debt.js          |     100 |      100 |     100 |     100 |                                           
 routes                 |     100 |      100 |     100 |     100 |                                           
  expenses.js           |     100 |      100 |     100 |     100 |                                           
  users.js              |     100 |      100 |     100 |     100 |                                           
------------------------|---------|----------|---------|---------|-------------------------------------------
Test Suites: 1 failed, 2 passed, 3 total
Tests:       7 passed, 7 total
Snapshots:   0 total
Time:        3.664 s
Ran all test suites.