Hydra: OpenID Connect Certification

[aeneasr]

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

[aeneasr]

• [x] Certification requires access to the userinfo endpoint which is tracked as #652
• [x] 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.