update for adding multiple members (#25128)

* update for adding multiple members

* fix unit test

* more test fixes

* add another unit test

* fix object passed by client4

* revert package-lock.json

* revert package-lock.json

* add length check

* limit size of lists in API requests

* revert package-lock

* add batching to front end

* add batching to front end

* fix bad merge

* update return type

* remove unnecessary permisssion check, add unit test

* fixes and add tests from review

* revert changes adding limits to other apis

* fixes

* clean-up from code review

* fix unit test call

* revert back to interface{}, fix unit test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/platform/client/src/client4.ts

@@ -1811,6 +1811,16 @@ export default class Client4 {
         );
     };
 
+    addToChannels = (userIds: string[], channelId: string, postRootId = '') => {
+        this.trackEvent('api', 'api_channels_add_members', {channel_id: channelId});
+
+        const members = {user_ids: userIds, channel_id: channelId, post_root_id: postRootId};
+        return this.doFetch<ChannelMembership[]>(
+            `${this.getChannelMembersRoute(channelId)}`,
+            {method: 'post', body: JSON.stringify(members)},
+        );
+    };
+
     addToChannel = (userId: string, channelId: string, postRootId = '') => {
         this.trackEvent('api', 'api_channels_add_member', {channel_id: channelId});