Add sentinel identityprovider on /auth

[akatranlp]

In this PR, the sentinel openid-provider will be mounted on /auth and will be used before keycloak to not depend on it.

THe following steps are needed to integrate the the new identity-provder:

• implement the authUserRepository from Sentinel
• implement the tokenSessionRepository from Sentinel
• add config options for secrets and other configuration
• mount the handler at the specified basePath and make it available
• migrate from keycloak to this ip
  • change middleware
  • change frontend

It is far from finished yet but a first version that can be inspected and is open for critic and first review.