Fix more subtle bugs with first_or_create

app/services/process_interaction_service.rb

@@ -62,7 +62,7 @@ class ProcessInteractionService < BaseService
   end
 
   def favourite!(xml, from_account)
-    status(xml).favourites.first_or_create!(account: from_account)
+    status(xml).favourites.where(account: from_account).first_or_create!(account: from_account)
   end
 
   def add_post!(body, account)

app/services/process_mentions_service.rb

@@ -14,7 +14,7 @@ class ProcessMentionsService < BaseService
         mentioned_account = follow_remote_account_service.("#{match.first}")
       end
 
-      mentioned_account.mentions.first_or_create(status: status)
+      mentioned_account.mentions.where(status: status).first_or_create(status: status)
     end
 
     status.mentions.each do |mentioned_account|