Permissions to promote a snapshot from a build workspace.

In my team when we end an iteration we want a snapshot of the stream, so we can right click on the stream to find the snapshots for all iterations.

The way we currently do this is to lock down the stream so no one can deliver until we get a build we are happy with and then take a snapshot.

Rather than do this we want to move to selecting the snapshot of the build workspace and promoting it to the stream.

The problem is that while I can do this as a jazz admin members of my team cannot. When they try they get an error message saying only the workspace owner (our build id) can promote.

I can't find a way in the process configuration to grant this authority to someone other than the workspace owner. What can I do to solve this problem?

Thanks
Alasdair