Preprints (?): Moderators should be redirected back to item page when adding a new author to an existing preprint

Is your feature request related to a problem? Please describe.

The current workflow for a moderator to add a new author to an existing preprint is confusing. At present, it proceeds as:

1. Add new author
2. After saving author entry, author page reloads to display a confirmation message and the same new author's data

However, the expectation would be that one would be redirected back to the item's manager view page (so one could see that the author had been added).

Describe the solution you'd like

Ideally for existing accounts:

• When adding via email lookup and the author's email is found, the moderator is redirected back to the item page, with a confirmation message; alternatively, they are given clear instructions that the author has been added and that they can edit their author details.
• When adding via filling in the form, the moderator is redirected back to the item page unless the user already has an account. In that case, the system should return the moderator to the author entry page upon save, then either a) fill in the current details on record and notify the moderator that they may need to update the details, or b) notify the moderator that XYZ are the current details and encourage them to change the details in the author form as needed.

The current message should stay the same if the moderator adds to the preprint an author who is already listed in the preprint.

Screenshots: Current flow and expectation for adding existing user as author

Expected:

or

No files or tests are named. Start by locating the moderator workflow for adding an author to an existing preprint and compare it with the current and expected flows in the issue screenshots. Done means the moderator returns to the item manager with confirmation for the specified account and form cases, while the existing-duplicate message remains unchanged.