Allow Transaction Modifications

[elliotcourant]

Transactions should be able to be modified with a PUT request to /bank_accounts/{bankAccountId}/transactions/{transactionId}.

If a transaction is from a manual link, then the following fields can be modified along with all the fields from the plaid version.

• Amount
• OriginalCategories (maybe just make these two fields match or just omit one?)
• Date
• AuthorizedDate
• OriginalName (Same logic with categories, do we want to maintain two fields for this for manual transactions?)
• IsPending

If a transaction was not created with a manual link, and was imported via Plaid then only the following fields can be modified:

• ExpenseId
• Categories
• Name
• MerchantName

A transaction cannot change its bank account.

Behaviors for expenses:

• When an expense is added to a transaction: Update the transaction's expenseId field, deduct the transaction's amount from the expense's current amount (do not go negative).
  • This has an inherent flaw: If a transaction is for $10, and then is spent from an expense with a current amount of $5, the expense's current amount becomes 0. In this moment the safe-to-spend is correct. But if the user were to remove the transaction from that expense; we would have no way of knowing that we should only return $5 of the $10 spent on the transaction to that expense. We would need to keep track of how much money was on the expense before a transaction was allocated to it in order to compensate for this.
• When a transaction is removed from an expense: Set the transaction's expenseId field to nil, return the amount of money spent from the expense to the expense's current amount. (see note above).
• When a transaction changes from expense A to B; combine the operations above as described.