Allow setting message when registering payment

[CherryDT]

Is your feature request related to a problem? Please describe.
When an external payment is manually registered using the "Pay now" button, there are only fields for payment method and amount but no additional notes/message field for saving payment details such as a payment transaction ID for future reference.

Describe the solution you'd like
I'd like there to be a "Message" field when registering a payment.

Additional context
I can see a column "Message" in the table after registering the payment, but it's empty and I don't have a way to set it... So I guess it shouldn't be too complicated to add it, as the field seemingly already exists in the DB? If I were to implement it myself, are there any gotchas to consider?

[pierredup]

The current message field is used to capture a message from the payment gateway after a payment has been made. Currently it's only used by paypal_express and is only populated when a payment fails, then it captures the failure details in the message field.

For this request, I would add 2 new fields: transaction_id varchar(255) and notes text.
The transaction_id can then be used to manually capture a transaction id, and the notes fields can be used for custom information when manually capturing a payment.

If I were to implement it myself, are there any gotchas to consider?

These additional fields should only be added when a payment is manually captured by an admin user, and not when the client initiates the payment. There are already a check in place to ensure a user is set when adding specific fields, so these new fields can be added in the same condition

SolidInvoice/src/PaymentBundle/Form/Type/PaymentType.php

Line 77 in b24e9aa

if (null !== $options['user']) {

[CherryDT]

When registering payment is allowed in the API, it should also be possible to add the comment.