[keycloak - OID4VCI] Create CredentialSignerProvider interface

[francis-pouatcha]

This is a proxy of:

• [OID4VCI] Create CredentialSignerProvider interface keycloak/keycloak#32953

[francis-pouatcha]

Related to :

• [OID4VCI] Create a CredentialBuilderProvider interface keycloak/keycloak#32951 being implemented by @IngridPuppet

[nitch2019]

Done from our side.
Waiting for KC to close the PR

[IngridPuppet]

To be more precise, the ticket depends on #8 to be closed first. But its PR is still pending:

• Offload format-specific credential building to dedicated credential builder providers (#32951) keycloak/keycloak#35046

[nitch2019]

Depending on #8

[IngridPuppet]

My progress is on this branch: https://github.com/adorsys/keycloak-oid4vc/tree/issue-32953-work
The multiple commits on the branch are intended to be squashed before creating the PR.

[nitch2019]

Waiting for the ticket to be merged at kc, then this can be closed here

[IngridPuppet]

Linked PR:

• Create credential signer providers to complement credential building keycloak/keycloak#36056

[IngridPuppet]

The issue with the pipeline has been addressed.