feat: Handle recording already started error

lang/main.json

@@ -508,6 +508,7 @@
         "onBy": "{{name}} started the live streaming",
         "pending": "Starting Live Stream...",
         "serviceName": "Live Streaming service",
+        "sessionAlreadyActive": "This session is already being recorded or live streamed.",
         "signedInAs": "You are currently signed in as:",
         "signIn": "Sign in with Google",
         "signInCTA": "Sign in or enter your live stream key from YouTube.",
@@ -772,6 +773,7 @@
         "serviceDescription": "Your recording will be saved by the recording service",
         "serviceDescriptionCloud": "Cloud recording",
         "serviceName": "Recording service",
+        "sessionAlreadyActive": "This session is already being recorded or live streamed.",
         "signIn": "Sign in",
         "signOut": "Sign out",
         "unavailable": "Oops! The {{serviceName}} is currently unavailable. We're working on resolving the issue. Please try again later.",

react/features/recording/middleware.js

@@ -261,6 +261,13 @@ function _showRecordingErrorNotification(recorderSession, dispatch) {
                 : 'recording.busyTitle'
         }));
         break;
+    case JitsiMeetJS.constants.recording.error.UNEXPECTED_REQUEST:
+        dispatch(showRecordingError({
+            titleKey: isStreamMode
+                ? 'liveStreaming.sessionAlreadyActive'
+                : 'recording.sessionAlreadyActive'
+        }));
+        break;
     default:
         dispatch(showRecordingError({
             descriptionKey: isStreamMode