Add LFK ci_unit_tests to projects on project_id

Changelog: changed

db/post_migrate/20220112230642_remove_projects_ci_unit_tests_project_id_fk.rb

+# frozen_string_literal: true
+
+class RemoveProjectsCiUnitTestsProjectIdFk < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  def up
+    with_lock_retries do
+      remove_foreign_key_if_exists(:ci_unit_tests, :projects, name: "fk_7a8fabf0a8")
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key(:ci_unit_tests, :projects, name: "fk_7a8fabf0a8", column: :project_id, target_column: :id, on_delete: "cascade")
+  end
+end

db/schema_migrations/20220112230642

+c528730414c1dcda5d312f03d4e37a0dbb51ebb0b0b87ada786cf686c358daa7
\ No newline at end of file

db/structure.sql

@@ -29384,9 +29384,6 @@ ALTER TABLE ONLY analytics_devops_adoption_snapshots
 ALTER TABLE ONLY lists
     ADD CONSTRAINT fk_7a5553d60f FOREIGN KEY (label_id) REFERENCES labels(id) ON DELETE CASCADE;
 
-ALTER TABLE ONLY ci_unit_tests
-    ADD CONSTRAINT fk_7a8fabf0a8 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY protected_branches
     ADD CONSTRAINT fk_7a9c6d93e7 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;
 

lib/gitlab/database/gitlab_loose_foreign_keys.yml

+---
 dast_site_profiles_pipelines:
   - table: ci_pipelines
     column: ci_pipeline_id
@@ -67,6 +68,10 @@ ci_project_mirrors:
   - table: namespaces
     column: namespace_id
     on_delete: async_delete
+ci_unit_tests:
+  - table: projects
+    column: project_id
+    on_delete: async_delete
 merge_requests:
   - table: ci_pipelines
     column: head_pipeline_id

spec/models/ci/unit_test_spec.rb

@@ -3,6 +3,11 @@
 require 'spec_helper'
 
 RSpec.describe Ci::UnitTest do
+  it_behaves_like 'cleanup by a loose foreign key' do
+    let!(:parent) { create(:project) }
+    let!(:model) { create(:ci_unit_test, project: parent) }
+  end
+
   describe 'relationships' do
     it { is_expected.to belong_to(:project) }
     it { is_expected.to have_many(:unit_test_failures) }