Transfer project from one user to another

Per this support request (and this slightly different issue):

Currently, the only way to transfer a project from one user to another is:

1. Create a dummy group for which both users are owners
2. Have the old user transfer ownership of the project from themselves to the group
3. Have the new user transfer ownership from the group to themselves
4. Delete the dummy group

It should be possible to do this directly, without the dummy group, along the lines of Github transfer requests.