do not issue deprecation warning on notify.type by default

Default configuration for notify.type is "none",
and prior to this change it was issuing the
deprecation warning which was not an intended
behaviour.

backend/app/cmd/server.go

@@ -354,7 +354,9 @@ func (s *ServerCommand) HandleDeprecatedFlags() (result []DeprecatedFlag) {
 		s.ImageProxy.HTTP2HTTPS = s.LegacyImageProxy
 		result = append(result, DeprecatedFlag{Old: "img-proxy", New: "image-proxy.http2https", Version: "1.5"})
 	}
-	if len(s.Notify.Type) != 0 && (len(s.Notify.Users) != 0 || len(s.Notify.Admins) != 0) {
+	if len(s.Notify.Type) != 0 && // explicitly empty, would likely never happen due to "none" default
+		!(len(s.Notify.Type) == 1 && contains("none", s.Notify.Type)) && // ignore default, "none" notify type
+		(len(s.Notify.Users) != 0 || len(s.Notify.Admins) != 0) { // new notify param(s) are used, safe to ignore the old one
 		s.handleDeprecatedNotifications()
 		result = append(result, DeprecatedFlag{Old: "notify.type", New: "notify.(users|admins)", Version: "1.9"})
 	}

backend/app/cmd/server_test.go

@@ -410,6 +410,7 @@ func TestServerApp_DeprecatedArgs(t *testing.T) {
 	p := flags.NewParser(&s, flags.Default)
 	args := []string{
 		"test",
+		"--notify.type=telegram",
 		"--auth.email.host=smtp.example.org",
 		"--auth.email.port=666",
 		"--auth.email.tls",