Disable unused package callback

Wrap  #update_composer_cache from the package model
in a feature flag to safely disable and then remove it.
It is a broken callback that is part of an incomplete
abandoned feature.

app/models/packages/package.rb

@@ -158,7 +158,7 @@ class Packages::Package < ApplicationRecord
     joins(:project).reorder(keyset_order)
   end
 
-  after_commit :update_composer_cache, on: :destroy, if: -> { composer? }
+  after_commit :update_composer_cache, on: :destroy, if: -> { composer? && Feature.disabled?(:disable_composer_callback) }
 
   def self.only_maven_packages_with_path(path, use_cte: false)
     if use_cte

config/feature_flags/development/disable_composer_callback.yml

+---
+name: disable_composer_callback
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64016
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/333587
+milestone: '14.0'
+type: development
+group: group::package
+default_enabled: false

spec/models/packages/package_spec.rb

@@ -1019,10 +1019,24 @@ RSpec.describe Packages::Package, type: :model do
       package.composer_metadatum.reload
     end
 
-    it 'schedule the update job' do
-      expect(::Packages::Composer::CacheUpdateWorker).to receive(:perform_async).with(project.id, package_name, package.composer_metadatum.version_cache_sha)
+    context 'with feature flag disabled' do
+      before do
+        stub_feature_flags(disable_composer_callback: false)
+      end
+
+      it 'schedule the update job' do
+        expect(::Packages::Composer::CacheUpdateWorker).to receive(:perform_async).with(project.id, package_name, package.composer_metadatum.version_cache_sha)
+
+        package.destroy!
+      end
+    end
 
-      package.destroy!
+    context 'with feature flag enabled' do
+      it 'does nothing' do
+        expect(::Packages::Composer::CacheUpdateWorker).not_to receive(:perform_async)
+
+        package.destroy!
+      end
     end
   end
 end