Clearing bank details #187442420

[tofarr]

• Isolates the before_save action for clearing bank details from the other before_saves
• Moves the before_save action into the base class to dry it up
• Fixes logic hole where bank details are not cleared if the payment_or_deposit_type has not changed (This will still not incur extra load unless there were actual bank details present - changing a nil to a nil as part of a save is a noop)
• Adds specs to cover this use case

[github-actions]

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