Add a new cop Database/DisableReferentialIntegrity

Add a cop to prevent usage of disable_referential_integrity
as this method can lead to data consistency problems and
create unsafe situations where triggers on all tables are
disabled.

.rubocop_todo/database/disable_referential_integrity.yml

+---
+Database/DisableReferentialIntegrity:
+  Exclude:
+    - 'spec/lib/gitlab/background_migration/cleanup_orphaned_lfs_objects_projects_spec.rb'

rubocop/cop/database/disable_referential_integrity.rb

+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Database
+      # Cop that checks if 'disable_referential_integrity' method is called.
+      class DisableReferentialIntegrity < RuboCop::Cop::Cop
+        MSG = <<~TEXT
+        Do not use `disable_referential_integrity`, disable triggers in a safe
+        transaction instead. Follow the format:
+          BEGIN;
+          ALTER TABLE my_table DISABLE TRIGGER ALL;
+          -- execute query that requires disabled triggers
+          ALTER TABLE my_table ENABLE TRIGGER ALL;
+          COMMIT;
+        TEXT
+
+        def_node_matcher :disable_referential_integrity?, <<~PATTERN
+          (send _ :disable_referential_integrity)
+        PATTERN
+
+        RESTRICT_ON_SEND = %i[disable_referential_integrity].freeze
+
+        def on_send(node)
+          return unless disable_referential_integrity?(node)
+
+          add_offense(node)
+        end
+      end
+    end
+  end
+end

spec/rubocop/cop/database/disable_referential_integrity_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+require_relative '../../../../rubocop/cop/database/disable_referential_integrity'
+
+RSpec.describe RuboCop::Cop::Database::DisableReferentialIntegrity do
+  subject(:cop) { described_class.new }
+
+  it 'does not flag the use of disable_referential_integrity with a send receiver' do
+    expect_offense(<<~SOURCE)
+      foo.disable_referential_integrity
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Do not use `disable_referential_integrity`, [...]
+    SOURCE
+  end
+
+  it 'flags the use of disable_referential_integrity with a full definition' do
+    expect_offense(<<~SOURCE)
+      ActiveRecord::Base.connection.disable_referential_integrity
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Do not use `disable_referential_integrity`, [...]
+    SOURCE
+  end
+
+  it 'flags the use of disable_referential_integrity with a nil receiver' do
+    expect_offense(<<~SOURCE)
+      class Foo ; disable_referential_integrity ; end
+                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Do not use `disable_referential_integrity`, [...]
+    SOURCE
+  end
+
+  it 'flags the use of disable_referential_integrity when passing a block' do
+    expect_offense(<<~SOURCE)
+      class Foo ; disable_referential_integrity { :foo } ; end
+                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Do not use `disable_referential_integrity`, [...]
+    SOURCE
+  end
+end