Change your email

1. In Settings, the person enters a code sent to the current inbox, then one sent to the new address.
2. The old address gets an email saying it changed.
3. Staff can correct the address of someone who has never signed in, from the desk; the invite goes out again to the new address.

Rules: once a person has signed in, nobody else can change their address. An address that already belongs to someone is refused, never merged.