server: qBittorrent: set tags after removing all existing tags

APIs of qBittorrent (removeTags, addTags) are incremental. However,
currently it is being used to "set" tags. As a result, tags are never
removed.

This change removes all existing tags before adding new set of tags
in order to simulate the idempotent set function.

server/services/qBittorrent/clientGatewayService.ts

@@ -179,9 +179,11 @@ class QBittorrentClientGatewayService extends ClientGatewayService {
   }
 
   async setTorrentsTags({hashes, tags}: SetTorrentsTagsOptions): Promise<void> {
-    return this.clientRequestManager
-      .torrentsAddTags(hashes, tags)
-      .then(this.processClientRequestSuccess, this.processClientRequestError);
+    return this.clientRequestManager.torrentsRemoveTags(hashes).then(() => {
+      this.clientRequestManager
+        .torrentsAddTags(hashes, tags)
+        .then(this.processClientRequestSuccess, this.processClientRequestError);
+    });
   }
 
   async setTorrentsTrackers({hashes, trackers}: SetTorrentsTrackersOptions): Promise<void> {

server/services/qBittorrent/clientRequestManager.ts

@@ -253,6 +253,20 @@ class ClientRequestManager {
       });
   }
 
+  async torrentsRemoveTags(hashes: Array<string>, tags?: Array<string>): Promise<void> {
+    return axios
+      .get(`${this.apiBase}/torrents/removeTags`, {
+        params: {
+          hashes: hashes.join('|'),
+          tags: tags?.join(','),
+        },
+        headers: {Cookie: await this.authCookie},
+      })
+      .then(() => {
+        // returns nothing
+      });
+  }
+
   async torrentsAddTrackers(hash: string, urls: Array<string>): Promise<void> {
     return axios
       .get(`${this.apiBase}/torrents/addTrackers?hash=${hash}&urls=${urls.join('|')}`, {