Send contribution receipt when contribution completed by recording payment on the backend
Through discussion in this PR, it has become clear that there is an inconsistency in which message templates are sent when completing a pending contribution with a payment, depending on where the payment is recorded.
If the payment is recorded via API and the receipt has not yet been set, a contribution receipt template is sent. If the payment is recorded via a Search Action and the receipt has not been sent, a contribution receipt template is sent. If the payment is recorded via Record Payment in the UI, there is an option to send to send a receipt, but if selected a "Additional Payment Receipt or Refund Notification" template is sent.
I think that in the third case, for consistency, we should send a contribution receipt template as long as the contribution is now completed. The same logic works with membership receipt templates.