Move away from shibboleth

[phavekes]

This issue is imported from pivotal

mijn*.eduid.nl uses shibd for authenticating. This causes an extra dependency on a server proces. And since shibd uses mysql for storing sessions, a dependency on a 2nd database platform. We only use verry simple authentication for mijn*.eduid.nl, so we should move to using oidc directly, without shibd.

Implement a generic Java Spring Boot library to be used by all Java apps. Depend on spring boot 3, this will require migrations for the Java apps which will use this library. See https://github.com/OpenConext/openconext-oidc-client