Add SkipLocal2FA option to pam and smtp sources (#17078)

* Add SkipLocal2FA option to other pam and smtp sources

Extend #16954 to allow setting skip local 2fa on pam and SMTP authentication sources

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

* make SkipLocal2FA omitempty

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

Co-authored-by: 6543 <6543@obermui.de>

services/auth/source/oauth2/source.go

@@ -25,7 +25,7 @@ type Source struct {
 	OpenIDConnectAutoDiscoveryURL string
 	CustomURLMapping              *CustomURLMapping
 	IconURL                       string
-	SkipLocalTwoFA                bool
+	SkipLocalTwoFA                bool `json:",omitempty"`
 
 	// reference to the loginSource
 	loginSource *login.Source