Initial description

Currently, pac4j configuration is done based off Magnolia YAML values. Maybe it would be easier (in the long run) to let pac4j be configured by its own config-by-file mechanism, as seen here: http://www.pac4j.org/4.3.x/docs/config.html

Ticket result

Thanks to the work done here, PD's SSO module is no longer coupled to Keycloak, but can be used with any 'OpenID Connect' Identity Provider. We have proved this in practice on the new cloud, where we have plugged the module to Okta. This is a big milestone for the module, making it ready to be published to the outside.