Feature Request: Auto Create Missing Users - Specify externally managed and initial role upon user creation.

[davmin]

With social login being able to create users now (thank you!) it makes sense to have a few more simple features around that i think.

• Option for automatically created users to be set to Externally Managed upon creation
• Initial role(s) to be granted upon creation
• disable the option to unlink account. maybe that button is meaningless since they would be linked upon next login anyway?

[lancepioch]

Please create this as a plugin, thank you.