[ ] add some warning flag for user to fill his e-mail address, when e-mail address was generated by us (in case there was no e-mail data returned from OAuth provider)
[x] there should be better handler for linking 2 existing accounts (let's imagine Acc A, with Google Token and Acc B, without one. When we try to link Acc B to the same Google Account, then we will have error. This error should be improved)
There are 2 things to be improved in this matter: