Repository Managers should be able to subscribe to Discussions

Is your feature request related to a problem? Please describe.
The existing Discussion feature is useful to facilitate communication between Repository Managers on a single Preprint under review. However as a Repository Manager, I do know know when there is ongoing Discussion because: a) the Discussion feature is exposed only at the Preprint level, and b) Managers do not receive alerts of new comments in Discussions where they are active (have made comments in the Discussion).

Describe the solution you'd like

Add a “Discussion” section on the Preprint Manager Dashboard: It should indicates how many active Discussions are ongoing in pending and published Preprints (including in which Preprints). It should also include a "My Discussions" which lists all Preprints with ongoing Discussions that the Manager has participated in, in reverse chronological order of recent activity.

Repository Managers should be able to “subscribe” to receive alerts of new Discussions on all or specific Preprints.

When a Repository Managers makes a comment in a Discussion, they should be automatically subscribed to receive alerts of all Future Discussions on a Preprint.

When a Repository Managers is “assigned” or “claims” a Preprint, they are automatically subscribed to receive alerts of all Discussions on a Preprint.

There should be some sort of alert in the Discussion of the Preprint's publication status changes, such as new version submission -- and Managers who are subscribed to that Discussion should receive those alerts as well.

There should also be some sort of alert in the Discussion of any new communication with the Preprint Owner (link to log).

There should also be an option for a Repository Manager to unsubscribe to the individual Discussion.

Additional context
Related: https://github.com/BirkbeckCTP/janeway/issues/3407

No files, tests, or entry points are identified. Start by reviewing the requested dashboard, subscription, and notification behavior together with related issue #3407; done means the requirements for discussion listings, subscriptions, and alerts are implemented across the described cases.