Better handling of duplicate definitions

It happens that users, through a game of copy/paste/import/page management, happen to create 2 definitions for the same requirement. The UI does everything possible to prevent this, but Confluence's APIs can't be hermetically plugged.

Fix situations in the UI

• Done in 1.13.5: Duplicates can be created when bulk-replacing keys in the editor. We'll send the list of keys to the server, and the server will respond with 409-CONFLICT and a message will be presented to the user, blocking them.

• Fixed a long time ago, duplicates appear in red after submitting the page: Duplicates can be created in the editor when the user avoids the RY macro, either by editing the HTML manually, either by pasting content.

Improve the back-end

• Done in 1.13.5: When a draft of requirement is created, we'll record the draft ID so users can go to the page and delete the requirement.

• Draft of requirements shouldn't be displayed in the search because it gives a feeling of corrupted database.

• Done in 1.13.5: As opposed to now, when a requirement is defined on 2 pages, we should record the links to the 2 pages.

• Done in 1.13.5: We'll use that to display the macro in bright red, both in the page and in the search results, and tell the user to fix the problem.

• Done in 1.13.5: When submitting the requirement excerpt, if it has a duplicate definition, we'll check whether it has disappeared from the original page.

This will give a better feeling of stability, although we're just putting checks in place to help the users manage their links properly.