PLT-4403 Add server-based channel autocomplete, search and paging (#4585)

* Add more channel paging API

* Add channel paging support to client

* Add DB channel search functions

* Add API for searching more channels

* Add more channel search functionality to client

* Add API for autocompleting channels

* Add channel autocomplete functionality to the client

* Move to be deprecated APIs to their own file

* Final clean-up

* Fixes related to feedback

* Localization changes

* Add unit as suffix to timeout constants

webapp/utils/async_client.jsx

@@ -239,6 +239,30 @@ export function getMoreChannels(force) {
     }
 }
 
+export function getMoreChannelsPage(offset, limit) {
+    if (isCallInProgress('getMoreChannelsPage')) {
+        return;
+    }
+
+    callTracker.getMoreChannelsPage = utils.getTimestamp();
+    Client.getMoreChannelsPage(
+        offset,
+        limit,
+        (data) => {
+            callTracker.getMoreChannelsPage = 0;
+
+            AppDispatcher.handleServerAction({
+                type: ActionTypes.RECEIVED_MORE_CHANNELS,
+                channels: data
+            });
+        },
+        (err) => {
+            callTracker.getMoreChannelsPage = 0;
+            dispatchError(err, 'getMoreChannelsPage');
+        }
+    );
+}
+
 export function getChannelStats(channelId = ChannelStore.getCurrentId(), doVersionCheck = false) {
     if (isCallInProgress('getChannelStats' + channelId) || channelId == null) {
         return;