🛂(backend) oidc userinfo endpoint json format

The userinfo endpoint can return 2 content types:
- application/json
- application/jwt

Gitlab oidc returns a json object, while
Agent Connect oidc returns a jwt token.
We are adapting the authentication to handle both cases.

CHANGELOG.md

@@ -9,6 +9,10 @@ and this project adheres to
 
 ## [Unreleased]
 
+## Fixed
+
+- 🐛 (backend) gitlab oicd userinfo endpoint #232
+
 
 ## [1.4.0] - 2024-09-17