Fixes commons-app#4278 "Media details categories editor: Category not actually added" (commons-app#4328)

* rectified category update

* changed class name, added javadoc

* javadoc

Author: 4D17Y4

data-client/src/main/java/org/wikipedia/csrf/CsrfTokenClient.java

@@ -6,6 +6,8 @@
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 
+import java.util.concurrent.Callable;
+import java.util.concurrent.Executors;
 import org.wikipedia.AppAdapter;
 import org.wikipedia.dataclient.Service;
 import org.wikipedia.dataclient.ServiceFactory;
@@ -142,7 +144,9 @@ public void error(@NonNull Throwable caught) {
                             AppAdapter.get().getPassword(), "");
                 }
 
-                Response<MwQueryResponse> response = service.getCsrfTokenCall().execute();
+                // Get CSRFToken response off the main thread.
+                Response<MwQueryResponse> response = Executors.newSingleThreadExecutor().submit(new CsrfTokenCallExecutor(service)).get();
+
                 if (response.body() == null || response.body().query() == null
                         || TextUtils.isEmpty(response.body().query().csrfToken())) {
                     continue;
@@ -210,4 +214,34 @@ public void twoFactorPrompt() {
     private interface RetryCallback {
         void retry();
     }
+
+    /**
+     * Class CsrfTokenCallExecutor which implement callable interface to get CsrfTokenCall.
+     */
+    class CsrfTokenCallExecutor implements Callable<Response<MwQueryResponse>> {
+
+        /**
+         * Service for token call.
+         */
+        private Service service;
+
+        /**
+         * Default Constructor.
+         * @param service
+         */
+        public CsrfTokenCallExecutor(Service service){
+            this.service = service;
+        }
+
+        /**
+         * Computes a result, or throws an exception if unable to do so.
+         *
+         * @return computed result
+         * @throws Exception if unable to compute a result
+         */
+        @Override
+        public Response<MwQueryResponse> call() throws Exception {
+            return service.getCsrfTokenCall().execute();
+        }
+    }
 }