[backend] feat(composer): source column for connector instance (#4313)

[antoinemzs]

Proposed changes

• Add source column to ConnectorInstance
• Default to "OTHER"; this value should be used as default so that inserts from other subsystems than the catalog or the properties migration mechanism don't imply that they were originated from the catalog or a migration

Testing Instructions

1. normal CRUD

Related issues

• Contributes to [EE] Deploy built-in integration from the catalog #4313

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality
• For bug fix -> I implemented a test that covers the bug

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.39%. Comparing base (04e2e56) to head (883de8c).

Additional details and impacted files

@@                  Coverage Diff                  @@
##             release/current    #4440      +/-   ##
=====================================================
- Coverage              50.39%   50.39%   -0.01%     
- Complexity              3721     3722       +1     
=====================================================
  Files                    912      913       +1     
  Lines                  27301    27305       +4     
  Branches                2046     2046              
=====================================================
+ Hits                   13758    13760       +2     
- Misses                 12707    12709       +2     
  Partials                 836      836              

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