Add effective_date field to transactions and update related logic

[jerry-enebeli]

This pull request introduces the concept of an "effective date" for transactions, which is used to determine the actual date a transaction should be considered effective, falling back to the creation date if not specified. This change impacts multiple files across the codebase, including models, database interactions, and tests.

Key changes include:

Model Updates:

• Added EffectiveDate field to RecordTransaction and Transaction structs in api/model/transaction.go and model/transaction.go respectively. [1] [2]
• Updated ToTransaction method in api/model/model.go to include the EffectiveDate field.
• Introduced GetEffectiveDate method in model/transaction.go to return the effective date or fall back to the creation date if not set.

Database Changes:

• Modified SQL queries in database/balance.go to use effective_date if available, otherwise fall back to created_at. [1] [2] [3]
• Updated RecordTransaction method in database/transaction.go to include effective_date in the insert statement.

Migration Script:

• Added a new migration script sql/1741007609.sql to add the effective_date column to the transactions table.

Test Updates:

• Updated test cases in database/transactions_test.go and transaction_test.go to account for the new effective_date field. [1] [2] [3] [4] [5] [6]