Correctly notify ACM users when their bank transfer is recieved

Similar to how our direct debit currently works. But we need to handle that the amount sent may not be right.

Start by comparing the existing direct-debit notification flow with the bank-transfer handling. Trace how received amounts are evaluated and how ACM users are notified, including the case where the transferred amount is incorrect. Done means the expected notification behavior is defined and covered for both matching and mismatched amounts.

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