This change allows to use the specified `username_attribute` in a search for group members. This can especially be useful in case the `uid` is used as the `username_attribute` and also in `member` or `uniqueMember` attribute of groups instead of the DN.
* Re-add example configuration for Crowd
* Implement Crowd authentication
* Fix: Some errors just mean there is no user
* Document crowd provider
* Vendor new dependencies
* Reduce error messages: Check for config details