Bug 1025779 - Generation (at POST /call-url)  and retrieval (GET /calls/{token}) of the call-url should require/provide an optional issuer parameter

I wonder if issuer and callerId shouldn't be both renamed to reflect what we are waiting for.

Sometimes issuer will be a Friendly name but it can be an email address as for callerId.

Maybe we should be waiting for "Friendly Name <email@address.io>" in both fields and rename issuer `callerId`.