fix breakout room multiple invitations

bigbluebutton-html5/imports/api/breakouts/server/handlers/breakoutJoinURL.js

@@ -15,13 +15,26 @@ export default function handleBreakoutJoinURL({ body }) {
     breakoutId,
   };
 
+  // only keep each users' last invitation
+  const newUsers = [];
+
+  const currentBreakout = Breakouts.findOne({ breakoutId }, { fields: { users: 1 } });
+
+  currentBreakout.users.forEach((item) => {
+    if (item.userId !== userId) {
+      newUsers.push(item);
+    }
+  });
+
+  newUsers.push({
+    userId,
+    redirectToHtml5JoinURL,
+    insertedTime: new Date().getTime(),
+  });
+
   const modifier = {
-    $push: {
-      users: {
-        userId,
-        redirectToHtml5JoinURL,
-        insertedTime: new Date().getTime(),
-      },
+    $set: {
+      users: newUsers,
     },
   };