social auth: Validate email in backends without get_verified_emails.
social auth: Validate email in backends without get_verified_emails.

If the social backend doesn't have get_verified_emails emails, and we
simply grab kwargs["details"].get("email") for the email, we should
still validate it is correct.
Needed for SAML. This will get covered by tests in upcoming commits that
add SAML support.

zulip/zulip,andersk/zulip,andersk/zulip,synicalsyntax/zulip,eeshangarg/zulip,brainwane/zulip,andersk/zulip,shubhamdhama/zulip,kou/zulip,zulip/zulip,rht/zulip,showell/zulip,timabbott/zulip,eeshangarg/zulip,rht/zulip,punchagan/zulip,punchagan/zulip,rht/zulip,brainwane/zulip,punchagan/zulip,kou/zulip,kou/zulip,zulip/zulip,synicalsyntax/zulip,andersk/zulip,eeshangarg/zulip,showell/zulip,timabbott/zulip,synicalsyntax/zulip,brainwane/zulip,hackerkid/zulip,showell/zulip,timabbott/zulip,synicalsyntax/zulip,hackerkid/zulip,punchagan/zulip,rht/zulip,timabbott/zulip,showell/zulip,shubhamdhama/zulip,punchagan/zulip,rht/zulip,hackerkid/zulip,eeshangarg/zulip,shubhamdhama/zulip,kou/zulip,eeshangarg/zulip,showell/zulip,kou/zulip,shubhamdhama/zulip,brainwane/zulip,shubhamdhama/zulip,punchagan/zulip,synicalsyntax/zulip,brainwane/zulip,synicalsyntax/zulip,shubhamdhama/zulip,rht/zulip,timabbott/zulip,zulip/zulip,kou/zulip,hackerkid/zulip,eeshangarg/zulip,showell/zulip,hackerkid/zulip,brainwane/zulip,synicalsyntax/zulip,hackerkid/zulip,shubhamdhama/zulip,brainwane/zulip,hackerkid/zulip,punchagan/zulip,timabbott/zulip,zulip/zulip,andersk/zulip,timabbott/zulip,zulip/zulip,rht/zulip,kou/zulip,andersk/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip,showell/zulip