Make namespace owner master of project upon creation

When an admin creates a project in the namespace of a user, that user
automatically gains master access to that project.

app/services/projects/create_service.rb

@@ -97,7 +97,8 @@ module Projects
       system_hook_service.execute_hooks_for(@project, :create)
 
       unless @project.group || @project.gitlab_project_import?
-        @project.team << [current_user, :master, current_user]
+        owners = [current_user, @project.namespace.owner].compact.uniq
+        @project.add_master(owners, current_user: current_user)
       end
 
       @project.group&.refresh_members_authorized_projects

changelogs/unreleased/tc-make-user-master-project-by-admin.yml

+---
+title: Ensure namespace owner is Master of project upon creation
+merge_request: 10910
+author:

spec/services/projects/create_service_spec.rb

@@ -27,6 +27,22 @@ describe Projects::CreateService, '#execute', services: true do
     end
   end
 
+  context "admin creates project with other user's namespace_id" do
+    it 'sets the correct permissions' do
+      admin = create(:admin)
+      opts = {
+        name: 'GitLab',
+        namespace_id: user.namespace.id
+      }
+      project = create_project(admin, opts)
+
+      expect(project).to be_persisted
+      expect(project.owner).to eq(user)
+      expect(project.team.masters).to include(user, admin)
+      expect(project.namespace).to eq(user.namespace)
+    end
+  end
+
   context 'group namespace' do
     let(:group) do
       create(:group).tap do |group|