Add a "Description" field to Spaces
Summary:
Ref T8377.
- Add a description field.
- Add edges so files can be attached.
Test Plan: {F492410}
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T8377
Differential Revision: https://secure.phabricator.com/D13235