Add support for Instant sepa payments

[janz93]

Add support for sepa instant transfers.
Sepa instant will be in October 2025 the new default.

Some prerequisite work is already present in the sepa_king gem. https://github.com/salesking/sepa_king/pull/117/files

Additional resources and what changes to the sepa transfer is already listed in the follow blogpost

Question:
Should the sepa instant replace the sepa transfer endpoint or should we create a new one?