EVEREST-1799 get groups claim and validate permissions

[recharte]

EVEREST-1799

Summary

This pull request implements support for validating RBAC permissions against user groups fetched from an external IDP. The changes address challenges with the current "sub"-based permissions validation by introducing group-based RBAC, as described in EVEREST-1799

Key Changes

OIDC Integration:

• Updated the OIDC flow to request the groups scope during authentication.
• Extracted the groups claim from the ID token if it is returned by the IDP.

RBAC Evaluation Logic:

• Extended the RBAC validation logic to check permissions against:
  • The user's sub ID.
  • Any groups the user belongs to (based on the groups claim).