Validate the batched background migrations dictionary

- Add a new rubocop to validate the `introduced_by_url`
  url

Changelog: added
Relates to: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/137970

db/docs/batched_background_migrations/backfill_finding_id_in_vulnerabilities.yml

@@ -2,7 +2,7 @@
 migration_job_name: BackfillFindingIdInVulnerabilities
 description: Backfills finding_id column on vulnerabilities table for a proper 1:1 relation
 feature_category: vulnerability_management
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/issues/418971
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/130058
 queued_migration_version: 20231116105945
 milestone: 16.4
 finalize_after: '2023-12-15'

rubocop/cop/background_migration/dictionary_file.rb

@@ -3,6 +3,8 @@
 require_relative '../../migration_helpers'
 require_relative '../../batched_background_migrations_dictionary'
 
+URL_PATTERN = %r{\Ahttps://gitlab\.com/gitlab-org/gitlab/-/merge_requests/\d+\z}
+
 module RuboCop
   module Cop
     module BackgroundMigration
@@ -11,6 +13,7 @@ class DictionaryFile < RuboCop::Cop::Base
         include MigrationHelpers
 
         MSG = {
+          invalid_url: "Invalid `%{key}` url for the dictionary. Please use the following format: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/XXX",
           missing_key: "Mandatory key '%{key}' is missing from the dictionary. Please add with an appropriate value.",
           missing_dictionary: <<-MESSAGE.delete("\n").squeeze(' ').strip
             Missing %{file_name}.
@@ -49,6 +52,10 @@ def on_class(node)
 
         private
 
+        def valid_url?(url)
+          url.match?(URL_PATTERN)
+        end
+
         def dictionary_file?(migration_class_name)
           File.exist?(dictionary_file_path(migration_class_name))
         end
@@ -67,6 +74,8 @@ def validate_dictionary_file(migration_name, node)
           return [:missing_key, { key: :finalize_after }] unless bbm_dictionary.finalize_after.present?
 
           return [:missing_key, { key: :introduced_by_url }] unless bbm_dictionary.introduced_by_url.present?
+
+          return [:invalid_url, { key: :introduced_by_url }] unless valid_url?(bbm_dictionary.introduced_by_url)
         end
 
         def rails_root

spec/rubocop/cop/background_migration/dictionary_file_spec.rb

@@ -134,7 +134,7 @@ def up
         end
 
         context 'with dictionary file' do
-          let(:introduced_by_url) { 'https://test_url' }
+          let(:introduced_by_url) { 'https://gitlab.com/gitlab-org/gitlab/-/merge_requests/132639' }
           let(:finalize_after) { '20230507160251' }
 
           before do
@@ -158,6 +158,25 @@ def up
             end
           end
 
+          context 'when the `introduced_by_url` is not correct' do
+            let(:introduced_by_url) { 'https://gitlab.com/gitlab-org/gitlab/-/merge_requests/132639/invalid' }
+
+            it 'throws offense on having a correct url' do
+              expect_offense(<<~RUBY)
+                class QueueMyMigration < Gitlab::Database::Migration[2.1]
+                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ #{format('Invalid `introduced_by_url` url for the dictionary. Please use the following format: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/XXX')}
+                  def up
+                    queue_batched_background_migration(
+                      'MyMigration',
+                      :users,
+                      :id
+                    )
+                  end
+                end
+              RUBY
+            end
+          end
+
           context 'with required dictionary keys' do
             it 'does not throw offense with appropriate dictionary file' do
               expect_no_offenses(<<~RUBY)