allow users to login with phone or email

It extends the client-first-message to specify identity type
(https://tools.ietf.org/html/rfc5802#section-5).
The extension attribute is "t". It's available values are:
1: for phone
2: for email
other value will be omitted.

Implementation notes:
1. just the scram mechanism supports phone/email login
2. just the odbc auth_method supports phone/email login

Other mechanisms/methods won't be used, they are planed to be removed