Allow for_namespace_monthly_usage for cross-db query

ee/app/models/ci/minutes/project_monthly_usage.rb

@@ -15,7 +15,7 @@ module Ci
         where(
           date: namespace_monthly_usage.date,
           project: namespace_monthly_usage.namespace.projects
-        )
+        ).allow_cross_joins_across_databases(url: 'https://gitlab.com/gitlab-org/gitlab/-/issues/343301')
       end
 
       def self.beginning_of_month(time = Time.current)

spec/support/database/cross-join-allowlist.yml

-- "./ee/spec/features/ci/ci_minutes_spec.rb"
 - "./ee/spec/features/merge_trains/two_merge_requests_on_train_spec.rb"
 - "./ee/spec/features/merge_trains/user_adds_merge_request_to_merge_train_spec.rb"
 - "./ee/spec/finders/ee/namespaces/projects_finder_spec.rb"