Assign doi task as non-admin

[f-necas]

Describe the bug
When a Reviewer (or less privileges) user tries to create a DOI, it only shows himself in task owner list.

To Reproduce
Steps to reproduce the behavior:

1. Add DOI to GN
2. Connect with a REVIEWER user
3. Make a DOI creation request
4. Only logged in user is listed.

Expected behavior
It should display the list of admin and reviewer (?) users.

Screenshots

Desktop (please complete the following information):

• GeoNetwork Version : 4.4.6

Same as #6152

[pmauduit]

The UI is requesting the /srv/api/users endpoint which returns every users only if the connected user is in the Administrator profile, otherwise:

• if the user is of UserAdmin profile, then the users of all groups where current user is of profile UserAdmin are returned.
• else, only the connected user is returned.

Related code here https://github.com/geonetwork/core-geonetwork/blob/main/services/src/main/java/org/fao/geonet/api/users/UsersApi.java#L136-L169

Maybe we should consider that reviewers of the group should be able to ask for a DOI creation request, so leveraging reviewers to useradmins for this specific call ? e.g. switching from:

        } else if (Profile.UserAdmin.equals(profile)) {

to:

        } else if (Profile.UserAdmin.equals(profile) || Profile.Reviewer.equals(profile)) {

But maybe in the default GN workflow, this was the reason for having a UserAdmin profiles in groups ?

[pmauduit]

I think the user interface might deserve a dedicated endpoint to add every relevant users to the list, instead of using /srv/api/users which is a bit restrictive.