Summary:
This diff adds support for an auth module. The module is used to provide
authentication and authorization (only user to role mappings). The module can
be written in any language and uses a simple protocol to communicate with
Memgraph.
Reviewers: teon.banek, buda
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D2359
