feat: Allow sorting collections in sidebar (#1870)

closes #1759

Co-authored-by: Tom Moor <tom.moor@gmail.com>

server/services/websockets.js

@@ -170,6 +170,7 @@ export default class Websockets {
               },
             ],
           });
+
         return socketio
           .to(
             collection.private
@@ -197,6 +198,16 @@ export default class Websockets {
           ],
         });
       }
+
+      case "collections.move": {
+        return socketio
+          .to(`collection-${event.collectionId}`)
+          .emit("collections.update_index", {
+            collectionId: event.collectionId,
+            index: event.data.index,
+          });
+      }
+
       case "collections.add_user": {
         // the user being added isn't yet in the websocket channel for the collection
         // so they need to be notified separately