[lib] refactor fetchFollowedFarcasterChannels

Summary: small refactor so that I can reuse code in next diff when I introduce fetchLedFarcasterChannels method

Test Plan: tested with next diff

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13293

lib/utils/neynar-client.js

@@ -117,7 +117,10 @@ class NeynarClient {
     return fids;
   }
 
-  async fetchFollowedFarcasterChannels(fid: string): Promise<NeynarChannel[]> {
+  async fetchFollowedFarcasterChannelsWithFilter(
+    fid: string,
+    filterFn: (channel: NeynarChannel) => boolean,
+  ): Promise<NeynarChannel[]> {
     const farcasterChannels = [];
     let paginationCursor = null;
 
@@ -144,7 +147,9 @@ class NeynarClient {
         const { channels, next } = json;
 
         channels.forEach(channel => {
-          farcasterChannels.push(channel);
+          if (filterFn(channel)) {
+            farcasterChannels.push(channel);
+          }
         });
 
         paginationCursor = next.cursor;
@@ -160,6 +165,10 @@ class NeynarClient {
     return farcasterChannels;
   }
 
+  fetchFollowedFarcasterChannels(fid: string): Promise<NeynarChannel[]> {
+    return this.fetchFollowedFarcasterChannelsWithFilter(fid, () => true);
+  }
+
   async fetchFarcasterChannelByName(
     channelName: string,
   ): Promise<?NeynarChannel> {