Jhbate/invite by key

@kentquirk could you take a look please. I still need to do a call,with a server token, to get the inviter user profile but that means a change to go-common 
Ok, just spoke with @HowardLook and we discussed both the email scenario and the signup scenario.  In the email scenario, the act of sending the email carries the equivalent risks to the PwD sending the email from their own email account.  We just happen to be generating and sending it on their behalf, so it is fine to have the name in there.

On the signup screen, it wasn't clear that having the name on the signup screen was going to cause an unauthenticated call to exist that provides access to the name of the person sending the invitation as well as who the invite was sent to.  While it is difficult to "brute force" the tokens, there are other ways that a token could be generated (a bug in an algorithm, etc.) and having the unauthenticated endpoint providing the information just opens us up to that risk.

Given that we *are* including the name of the individual in the email and that the person who is signing up likely got to the signup page from that email, there is not as much necessity for having the name on the actual signup page.  From a customer experience standpoint, they will know why they are at the signup page because of the invite and once they successfully sign up, they will see who sent the invite such that they can accept.

Given that, can we remove this unauthenticated endpoint?