Datev deployment: Extract changes on a JAR

[hugoib]

Current DATEV deployment is customised in regards to the main branch.

The customisations need to be either extracted on a JAR or integrated into a KC stable version.

This ticket is to track that.

First step.- Sync about the status, ask Francis.

[IngridPuppet]

Resolution with Mr @francis-pouatcha:

• Move the current custom code for OpenID4VP authentication into a plugin.
• The solution around an identity provider or token exchange will be investigated later.

[Ogenbertrand]

Estimated for 3 days.