Approves requests to join a group.
Note: This function is only relevant for private groups.
The approvejoinGroupRequests() function returns a Promise that resolves when a site member's request to join a group is approved.
Only site admins and group admins can approve site member requests to join a group, unless the group setting, membersCanApprove is set to true.
ID of the group requested to join.
IDs of the site members to approve.