Preprints: Moderators should be able to claim or assign preprints

Is your feature request related to a problem? Please describe.
As a Repository Administrator, I would like to assign individual moderators, or groups of moderators, a preprint based on their expertise. I also expect that the assigned moderator(s) will receive a notification of assignment when I assign them to a preprint.

As a Repository Manager, I would like to claim a preprint to indicate that I am currently reviewing it. I would also like to remove from my claim list any preprints I feel incorrectly assigned to me. Finally, I expect my Moderator Dashboard to be filtered to display only the preprints claimed by me or assigned to my group; and I should be able to remove the filter to show all active and/or unclaimed preprints.

Describe the solution you'd like

Add a new option at the preprint level: assigned moderator.

A Manager/Moderator should be able to pick from a drop-list of fellow Moderators/Managers to assign it to that user's queue. The option and pick list should be visible in both the Repository Manager Dashboard and the Repository Manager Item View.

In an ideal version, articles would be able also be assigned to a group of Moderators, e.g. Subject Matter Experts, Language Speakers, and then claimed by one of the Moderators in such group.

Once claimed/assigned:

• The Pending Preprints queue would be split into “Unclaimed/Unassigned Preprints” and “Claimed/Assigned Preprints”;
• The Assigned Moderator would be clearly indicated in the Repository Manager View for that Preprint and in the “Claimed/Assigned Preprints” listing;
• If a Claimed/Assigned Moderator is assigned, only they (+ and the Manager, if that role exists https://github.com/BirkbeckCTP/janeway/issues/3498 ) would receive a notification about a new version submission;
• If a Moderator who is not the Claimed/Assigned Moderator has communication with the Submitting Author (Preprint Owner), the Claimed/Assigned Moderator would be copied.
• After a Preprint or a New Verison is Published, the Claimed/Assigned Moderator should have the option to remove themselves as Claimed/Assigned Moderator for the Preprint (alternatively: they should be automatically removed).

Tech notes

• We can have a m2m relationship between a preprint and moderators(core.models.Account) + a claim system similar to that of typesetting plugin
• Subjects could also have a m2m to moderators, and the claim/assign interface would let you pick either moderators or subjects that have moderators linked to them.

Start by reading the typesetting plugin's claim system and core.models.Account, then inspect the Repository Manager Dashboard and Repository Manager Item View mentioned in the request. Map the moderator assignment, claiming, filtering, notification, and version-publication behavior before determining the affected preprint workflow and tests; done means the requested assignment and claim states work consistently across those views.