FEATURE: bulk remove tags (#10831)

https://meta.discourse.org/t/bulk-actions-remove-tags-in-addition-to-change-tags/52145

lib/topics_bulk_action.rb

@@ -13,7 +13,8 @@ class TopicsBulkAction
   def self.operations
     @operations ||= %w(change_category close archive change_notification_level
                        reset_read dismiss_posts delete unlist archive_messages
-                       move_messages_to_inbox change_tags append_tags relist)
+                       move_messages_to_inbox change_tags append_tags remove_tags
+                       relist)
   end
 
   def self.register_operation(name, &block)
@@ -176,6 +177,15 @@ class TopicsBulkAction
     end
   end
 
+  def remove_tags
+    topics.each do |t|
+      if guardian.can_edit?(t)
+        TopicTag.where(topic_id: t.id).delete_all
+        @changed_ids << t.id
+      end
+    end
+  end
+
   def guardian
     @guardian ||= Guardian.new(@user)
   end