Remove disk source configuration

This is a follow-up issue to #282 (closed)

The remaining tasks are pending in order to completely remove disk source configuration

Pages configuration switch API/disc source gitlab#210010 (closed) in %13.0
Remove code for disk config source TODO %13.2 or %13.3
New version without the disk config source deployed to production TODO %13.2 or %13.3

Edited Apr 23, 2020 by Jaime Martinez