Improve @mention regex

app/services/process_hashtags_service.rb

@@ -4,7 +4,7 @@ class ProcessHashtagsService < BaseService
       tags = status.text.scan(Tag::HASHTAG_RE).map(&:first)
     end
 
-    tags.map(&:downcase).each do |tag|
+    tags.map(&:downcase).uniq.each do |tag|
       status.tags << Tag.where(name: tag).first_or_initialize(name: tag)
     end
   end