Add setting to OAuth handlers to skip local 2FA authentication (#16594)

This PR adds a setting to OAuth and OpenID login sources to allow the source to
skip local 2FA authentication.

Fix #13939

Signed-off-by: Andrew Thornton <art27@cantab.net>

services/auth/source/oauth2/source.go

@@ -24,6 +24,7 @@ type Source struct {
 	OpenIDConnectAutoDiscoveryURL string
 	CustomURLMapping              *CustomURLMapping
 	IconURL                       string
+	SkipLocalTwoFA                bool
 
 	// reference to the loginSource
 	loginSource *models.LoginSource