User should exist in the local directory after successful authentication

Scenario: JIRA -> Crowd -> LDAP Delegated Auth

1. New user is created in LDAP.
2. New user tries to log in in JIRA.

-> Authentication succeeds, and the new user is created in Crowd, but will not be visible in JIRA before the next synchronisation with Crowd.

The specific problem is that DBCachingRemoteDirectory#authenticate does not create non-existing users in the local directory.

Ideally we would do full synchronisation in this case, but a full synchronisation can take a very long time. Creating user in the local directory and adding group memberships for the user should fix this situation.