Remove package_already_taken validation from Maven

Validating that two projects could not have the same package
name for Maven projects was causing problems when users
used one project to create packages for other projects
using CI. The validation is being removed from Maven.

ee/app/models/packages/package.rb

@@ -13,7 +13,7 @@ class Packages::Package < ApplicationRecord
     format: { with: Gitlab::Regex.package_name_regex }
 
   validate :valid_npm_package_name, if: :npm?
-  validate :package_already_taken
+  validate :package_already_taken, if: :npm?
 
   enum package_type: { maven: 1, npm: 2 }
 

ee/changelogs/unreleased/13175-400-bad-request-when-deploying-a-maven-package.yml

+---
+title: Change package validation scope to fix Maven package naming functionality
+merge_request: 14922
+author:
+type: fixed

ee/spec/models/packages/package_spec.rb

@@ -15,6 +15,28 @@ RSpec.describe Packages::Package, type: :model do
       it { is_expected.to allow_value("my.app-11.07.2018").for(:name) }
       it { is_expected.not_to allow_value("my(dom$$$ain)com.my-app").for(:name) }
     end
+
+    describe '#package_already_taken' do
+      context 'npm package' do
+        let!(:package) { create(:npm_package) }
+
+        it 'will not allow a package of the same name' do
+          new_package = build(:npm_package, name: package.name)
+
+          expect(new_package).not_to be_valid
+        end
+      end
+
+      context 'maven package' do
+        let!(:package) { create(:maven_package) }
+
+        it 'will allow a package of the same name' do
+          new_package = build(:maven_package, name: package.name)
+
+          expect(new_package).to be_valid
+        end
+      end
+    end
   end
 
   describe '.by_name_and_file_name' do