Added integration with OpenID Connect Authelia

[arbdevml]

No description provided.

[triplem]

This PR would only allow authelia in the future. Why not just use the keycloak way only?

[arbdevml]

Why not just use the keycloak way only?

Because this plugin has to support OpenID providers as many as possible.

This PR would only allow authelia in the future.

One row was updated only in this pull request.
This pull request didn't remove the support of Keycloak.

Before update:
177: if access_token? # keycloak way...
After update:
191: if (access_token? && access_token.exclude?('authelia')) # keycloak way...

Explanation:
if condition true (access_token? && access_token.exclude?('authelia'))
it means the OpenID provider is Keycloak
else have to use another provider like Authelia.

Could you review this pull request, please.
Could you explain why you don't want to apply this pull request, please?

[arbdevml]

triplem, is there any issues with it, or should I add something?