Allow the user to provide email / phone number if those are absent from OAuth user info

For example, Facebook does not define a scope to retrieve phone number.

Some application may expect all user to have email to contact with.

One approach to solve this is to prompt the user to add a Email / Phone login ID if email / phone is absent from OAuth user info. This step is part of the signup interaction.

No files, tests, or entry points are identified in the issue, so start by locating the signup interaction and the OAuth user-info handling. The work is done when users whose OAuth data lacks an email or phone number can provide a login ID during signup.

Written by the indexing model from the issue text.