Migrate Relationship endpoints from Drupal

There are still additional endpoints to migrate under the account/profile/{username} path. Some of these paths include: /projects, /eca, /forum, /mailing-list, and /gerrit

The spec: https://api.eclipse.org/#operation/ProjectRelationship

The service will most likely need to connect to the Gerrit API, as well as make use of our mailing-list-api.