Add PWA, service worker and Web Push

- Use new notification request/opt-in flow for push
- Implement unsubscribing
- Implement muting
- Implement emojis in title
- Add iOS specific PWA warning
- Don’t use websockets when web push is enabled
- Fix duplicate notifications
- Implement default web push setting
- Implement changing subscription type
- Implement web push subscription refresh
- Implement web push notification click

server/server_middleware.go

@@ -58,6 +58,15 @@ func (s *Server) ensureWebEnabled(next handleFunc) handleFunc {
 	}
 }
 
+func (s *Server) ensureWebPushEnabled(next handleFunc) handleFunc {
+	return func(w http.ResponseWriter, r *http.Request, v *visitor) error {
+		if !s.config.WebPushEnabled {
+			return errHTTPNotFound
+		}
+		return next(w, r, v)
+	}
+}
+
 func (s *Server) ensureUserManager(next handleFunc) handleFunc {
 	return func(w http.ResponseWriter, r *http.Request, v *visitor) error {
 		if s.userManager == nil {