Add foreign key from web_hooks to groups

This foreign key constraint prevents creating inconsistent records.

changelogs/unreleased/202423-foreign-key-webhooks-groups.yml

+---
+title: Add foreign key from web_hooks to groups
+merge_request: 57735
+author:
+type: other

db/migrate/20210325092215_add_not_valid_foreign_key_to_group_hooks.rb

+# frozen_string_literal: true
+
+class AddNotValidForeignKeyToGroupHooks < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def up
+    with_lock_retries do
+      add_foreign_key :web_hooks, :namespaces, column: :group_id, on_delete: :cascade, validate: false
+    end
+  end
+
+  def down
+    with_lock_retries do
+      remove_foreign_key_if_exists :web_hooks, column: :group_id
+    end
+  end
+end

db/schema_migrations/20210325092215

+ea819fd401c5566986fd495ed3b8aa0d296d6c9e3fedf2a10f34cb7fbaeedb20
\ No newline at end of file

db/structure.sql

@@ -26571,6 +26571,9 @@ ALTER TABLE ONLY requirements_management_test_reports
 ALTER TABLE ONLY pool_repositories
     ADD CONSTRAINT fk_rails_d2711daad4 FOREIGN KEY (source_project_id) REFERENCES projects(id) ON DELETE SET NULL;
 
+ALTER TABLE ONLY web_hooks
+    ADD CONSTRAINT fk_rails_d35697648e FOREIGN KEY (group_id) REFERENCES namespaces(id) ON DELETE CASCADE NOT VALID;
+
 ALTER TABLE ONLY group_group_links
     ADD CONSTRAINT fk_rails_d3a0488427 FOREIGN KEY (shared_group_id) REFERENCES namespaces(id) ON DELETE CASCADE;
 

spec/db/schema_spec.rb

@@ -87,7 +87,6 @@ RSpec.describe 'Database schema' do
     users_star_projects: %w[user_id],
     vulnerability_identifiers: %w[external_id],
     vulnerability_scanners: %w[external_id],
-    web_hooks: %w[group_id],
     web_hook_logs_part_0c5294f417: %w[web_hook_id]
   }.with_indifferent_access.freeze