Account merging: handle duplicates for TagFollowing

I missed it in #7803

closes #7807

Changelog.md

@@ -3,6 +3,7 @@
 ## Refactor
 * Add unique index to poll participations on `poll_id` and `author_id` [#7798](https://github.com/diaspora/diaspora/pull/7798)
 * Add 'completed at' date to account migrations [#7805](https://github.com/diaspora/diaspora/pull/7805)
+* Handle duplicates for TagFollowing on account merging [#7807](https://github.com/diaspora/diaspora/pull/7807)
 
 ## Bug fixes
 

app/models/account_migration.rb

@@ -194,6 +194,10 @@ class AccountMigration < ApplicationRecord
       .joins("INNER JOIN contacts as c2 ON (contacts.person_id = c2.person_id AND contacts.user_id=#{old_user.id} AND"\
         " c2.user_id=#{new_user.id})")
       .destroy_all
+    TagFollowing
+      .joins("INNER JOIN tag_followings as t2 ON (tag_followings.tag_id = t2.tag_id AND"\
+        " tag_followings.user_id=#{old_user.id} AND t2.user_id=#{new_user.id})")
+      .destroy_all
   end
 
   def update_person_references

spec/models/account_migration_spec.rb

@@ -210,6 +210,11 @@ describe AccountMigration, type: :model do
           user:   new_person.owner,
           person: FactoryGirl.create(:contact, user: old_person.owner).person
         )
+        FactoryGirl.create(
+          :tag_following,
+          user: new_person.owner,
+          tag:  FactoryGirl.create(:tag_following, user: old_person.owner).tag
+        )
       end
 
       it "runs without errors" do