Expanding user groups while searching for issues

While using the “/rest/api/3/user” endpoint, I can use the “groups” values for the “expand” parameter and get the groups of the user.

Can I do the same while searching for issues?

The “/rest/api/3/search” endpoint seems to be returning user objects for assignee and reporter field values. Can I expand that search endpoint response to include the groups of assignee, reporter, or other user custom fields? If yes, what would be the expand token for it?

If that is not possible, is there a way to get the groups of more than one user in a single REST call?