Auth: Add validation to Generic OAuth API and UI (#81345)

* wip

* Update validation

* Chore: Remove InputControl usage

* Fixes, validation

* Remove empty option

* Validation changes

* Add tests, rename

* lint

---------

Co-authored-by: Clarity-89 <homes89@ukr.net>

pkg/services/ssosettings/errors.go

@@ -10,6 +10,14 @@ var (
 
 	ErrNotConfigurable = errNotFoundBase.Errorf("not configurable")
 
+	ErrBaseInvalidOAuthConfig = errutil.ValidationFailed("sso.invalidOauthConfig")
+
+	ErrInvalidOAuthConfig = func(msg string) error {
+		base := ErrBaseInvalidOAuthConfig.Errorf("OAuth settings are invalid")
+		base.PublicMessage = msg
+		return base
+	}
+
 	ErrInvalidProvider = errutil.ValidationFailed("sso.invalidProvider", errutil.WithPublicMessage("Provider is invalid"))
 	ErrInvalidSettings = errutil.ValidationFailed("sso.settings", errutil.WithPublicMessage("Settings field is invalid"))
 	ErrEmptyClientId   = errutil.ValidationFailed("sso.emptyClientId", errutil.WithPublicMessage("ClientId cannot be empty"))