Support accepting an invitation when the email is not bound to the current account. Web: <img width="427" alt="image" src="https://user-images.githubusercontent.com/9841565/126120297-a75eecae-27ae-497a-84c7-1538c61b7585.png"> - [ ] Find where to put the invite in UI - [ ] Accept the invite by binding the email to the account (accept IS terms + email verification) - [ ] Or accept without binding (identity/api/v2/sign-ed25519) ~3d