Context:
As discussed with FE and PM, we no longer require the check that prohibits users who are not the owner of a process to edit the digest. Instead, any logged in user who can view a specific process on the processes page is allowed to edit the digest. 
However, if no owner is set then the digest editing should be prohibited - we will disable the controls in the UI but it might be sensible to also add a BE check for this.

AT:

• anybody can edit digests, not just owners
• if no owner is set, digest cannot be enabled/edited