Add user_id info for several metrics

[JeremyReynard]

What

Add user_id info for several metrics :

• keycloak_logins
• keycloak_failed_login_attempts
• keycloak_registrations
• keycloak_registrations_errors

Verification Steps

Launch the PrometheusExporterTest file

Checklist:

• [X] Code has been tested locally by PR requester
• [X] Changes have been successfully verified by another team member

Progress

• [x] Finished task

[pb82]

I think this could cause problems similar to #64 or #63 when there is a large number of users.

[pb82]

Closing this, as we should not add user_id to the labels (causes excessive metrics bloat).