The command arguments should be a host:port pair and an index builder UUID. It should be a primary only internal user command and only accept majority write concern.

Depends on SERVER-37636 to set up the index build interface into which this command will hook. The function on the interface can just return Status::OK() for now, and have this command call it.

The function should take the host:port pair and index builder UUID, with which it will eventually identify the correct builder to which to pass the host:port pair.