add isTrackingMembers flag to know if EncryptionUsers have been written

for this room

src/matrix/room/Room.js

@@ -260,6 +260,10 @@ export class Room extends EventEmitter {
         return !!this._summary.encryption;
     }
 
+    get isTrackingMembers() {
+        return this._summary.isTrackingMembers;
+    }
+
     async _getLastEventId() {
         const lastKey = this._syncWriter.lastMessageKey;
         if (lastKey) {

src/matrix/room/RoomSummary.js

@@ -147,6 +147,7 @@ class SummaryData {
         this.heroes = copy ? copy.heroes : null;
         this.canonicalAlias = copy ? copy.canonicalAlias : null;
         this.hasFetchedMembers = copy ? copy.hasFetchedMembers : false;
+        this.isTrackingMembers = copy ? copy.isTrackingMembers : false;
         this.lastPaginationToken = copy ? copy.lastPaginationToken : null;
         this.avatarUrl = copy ? copy.avatarUrl : null;
         this.notificationCount = copy ? copy.notificationCount : 0;
@@ -238,6 +239,10 @@ export class RoomSummary {
         return this._data.hasFetchedMembers;
     }
 
+    get isTrackingMembers() {
+        return this._data.isTrackingMembers;
+    }
+
     get lastPaginationToken() {
         return this._data.lastPaginationToken;
     }
@@ -262,6 +267,13 @@ export class RoomSummary {
         return data;
     }
 
+    writeIsTrackingMembers(value, txn) {
+        const data = new SummaryData(this._data);
+        data.isTrackingMembers = value;
+        txn.roomSummary.set(data.serialize());
+        return data;
+    }
+
 	writeSync(roomResponse, membership, isInitialSync, isTimelineOpen, txn) {
         // clear cloned flag, so cloneIfNeeded makes a copy and
         // this._data is not modified if any field is changed.