[IMP] internal_transfer_with_agreed_amount: modify write vals in one method i#24002

[CLaurelB]

Modify in a single method the values that will be written in the account move lines so that the method can be inherited in case it is necessary to modify more values in the lines.

In addition, two methods are added to pre and post process payments, to be used if modifications are required in an inheritance.

Finally, obtaining currencies related to the internal transfer have been moved to a separate method to facilitate the inheritance of the method that validates the number of currencies.

Changelog:

• Set debit and credit values to write in _prepare_values_from_lines method when the exchange currency is the same as the company currency.
• Add methods to be inherited when payments also needs modifications.
• Get the currencies in a new method named _get_currencies.

[CLaurelB]

@rolandojduartem could you review, please?

[CLaurelB]

@rolandojduartem could you review again, please?

[luisg123v]

Missing task ID on MR title

[CLaurelB]

Missing task ID on MR title

Since it's related to a ticket, I added the ticket ID on the title.

[CLaurelB]

@luisg123v could you review again, please?