User mapping - FE - reassign banners

This issue is a placeholder for implementing the banners the user should see after accepting/rejecting the reassignment

Banner designs

Implementation notes

All the actions (cancel, approve, reject) should redirect to the groups dashboard, as opposed to the acceptance/approval redirecting to the page of the specific group. The rationale is that if the user is not already be a member of the group then the acceptance alert will not have access to data like destination_group and other data we need from the import_source_user table to do things like to yourself on { imported top level group }.