Implement review comments from @DouweM for !10467.28695-move-all-associated-records-to-ghost-user

1. Have `MigrateToGhostUser` be a service rather than a mixed-in module, to keep
   things explicit. Specs testing the behavior of this class are moved into a
   separate service spec file.

2. Add a `user.reported_abuse_reports` association to make the
   `migrate_abuse_reports` method more consistent with the other `migrate_`
   methods.

1 files changed, 1 insertions, 0 deletions

diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 6a787f6b0df..3f9c013ce37 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -36,6 +36,7 @@ describe User, models: true do
     it { is_expected.to have_many(:pipelines).dependent(:nullify) }
     it { is_expected.to have_many(:chat_names).dependent(:destroy) }
     it { is_expected.to have_many(:uploads).dependent(:destroy) }
+    it { is_expected.to have_many(:reported_abuse_reports).dependent(:destroy).class_name('AbuseReport') }
 
     describe "#abuse_report" do
       let(:current_user) { create(:user) }