FEATURE: Add user to topic_tags_changed event (#28714)

* FEATURE: Add user to topic_tags_changed event

Add user to topic_tags_changed event context
Update automation plugin with new arguments in event
Update tests for new arguments

relates to https://github.com/discourse/discourse-chat-integration/pull/214

* DEV: change variable name for better readability

changed `tags` to be payload and used `values_at` to get the values of the keys

lib/discourse_tagging.rb

@@ -212,6 +212,7 @@ module DiscourseTagging
         topic,
         old_tag_names: old_tag_names,
         new_tag_names: topic.tags.map(&:name),
+        user: guardian.user,
       )
 
       true