OpenID Connect Certification

[aeneasr]

This issue keeps track of the OpenID Connect certification process. Current progress:

[aeneasr]

• Certification requires access to the userinfo endpoint which is tracked as oauth2: Support userinfo endpoint #652
• Certification requires allowing sending client secrets via POST -> fosite
• Support acr value: No acr value present in the ID Token [The acr value in the ID Token]
• Check how we can support prompt
• Check how we can support max-age
• Error codes need to be adopted to OpenID Connect conformity for reusing authorize codes

[aeneasr]

[aeneasr]

All required self-service tests pass now.