This aligns the search filter escaping to [RFC4515](https://tools.ietf.org/search/rfc4515).
`base.ldif` has also been updated to be a closer match to RFC 2307.
* [BUGFIX] Set username retrieved from authentication backend in session.
In some setups, binding is case insensitive but Authelia is case
sensitive and therefore need the actual username as stored in the
authentication backend in order for Authelia to work correctly.
Fixes#561.
* Use uid attribute as unique user identifier in suites.
* Fix the integration tests.
* Update config.template.yml
* Compute user filter based on username attribute and users_filter.
The filter provided in users_filter is now combined with a filter
based on the username attribute to perform the LDAP search query
finding a user object from the username.
* Fix LDAP based integration tests.
* Update `users_filter` reference examples
