Add composer pull_package event

lib/api/composer_packages.rb

@@ -161,6 +161,8 @@ module API
 
           not_found! unless metadata
 
+          track_package_event('pull_package', :composer)
+
           send_git_archive unauthorized_user_project.repository, ref: metadata.target_sha, format: 'zip', append_sha: true
         end
       end

spec/requests/api/composer_packages_spec.rb

@@ -434,6 +434,7 @@ RSpec.describe API::ComposerPackages do
           end
 
           it_behaves_like 'process Composer api request', params[:user_role], params[:expected_status], params[:member]
+          it_behaves_like 'a package tracking event', described_class.name, 'pull_package'
         end
       end
     end