ISAICP-6321: Allow revision access to non moderator users.

[idimopoulos]

No description provided.

[pfrenssen]

This came back from UAT with some suggestion to update the scope of this ticket (ref. comments in the Jira ticket). This resulted in some necessary changes to the workflow:

• All members are now allowed to transition content from validated to proposed, but the button label needs to be different in case the transition is done by a facilitator (= Request changes) or the original author of the content (= Propose changes). I implemented an event that allows to alter the button labels dynamically: StateMachineButtonLabelsEvent.
• In the case of pre-moderated content, we should send out different notications to the collection owner and the content author when the transition from validated to proposed is executed. An owner should get a message that "content is proposed for publication" while the content author should still get the existing message "a facilitator has requested you to modify the content".
• This also means that the workflow is now different between pre-moderated and post-moderated collections. This caused failures for members with the author role. Beforehand we were handling this role by dynamically swapping an author from pre-moderated to post-moderated, but this is no longer possible. If an author is pretended to be post-moderated, then these changes to the pre-moderated workflow are no longer taking effect. It took some time to unravel this, but I was able to solve it by removing the workaround with the publish content in moderated groups permission and replacing it with standard transition permissions and updating the joinup_community_content.permission_scheme file. It is now handled in the same way as how a facilitator is being able to transition content to validated state.

I tried to order the commits for this latest round of changes in a logical way to make it easier to review. The commits are starting on March 19 (commit ea90a0a6):

1. First (to warm up) the small fixes + API additions that I did during the session.
2. I understood that discussions are always post-moderated after a discussion with @idimopoulos. Added a bunch of comments and updated test coverage of this ticket. This was also not handled correctly in the first iteration of this PR, but is now fixed. (commit 1cf025ad26)
3. A commit to get a green build again after the removal of the author role publish content in moderated groups workaround. I wanted to get a green build before doing the next 2 steps. These are the final changes that complete the removal of the workaround. Commit 7ebb654e9.
4. Add a failing test for the notifications that should now be sent. Commit 583f4af.
5. The implementation of the notifications in a single commit, turning the test green. Commit 6eaee3d.
6. Add a failing test for the changing of the button from Request changes to Propose changes. Commit bb34143e4.
7. Implement the changing of the button label + 1 additional commit to make the tests green again (I had a small bug in the test). Last 2 commits.