Fix race condition on container repository create

Return the existing container repository if
creation fails due to invalid record or
uniqueness constraint error.

Changelog: fixed

app/models/container_repository.rb

@@ -154,6 +154,8 @@ class ContainerRepository < ApplicationRecord
 
   def self.create_from_path!(path)
     build_from_path(path).tap(&:save!)
+  rescue ActiveRecord::RecordNotUnique, ActiveRecord::RecordInvalid
+    self.find_by_path!(path)
   end
 
   def self.build_root_repository(project)

spec/models/container_repository_spec.rb

@@ -281,6 +281,16 @@ RSpec.describe ContainerRepository do
         expect(repository.name).to be_empty
       end
     end
+
+    context 'when repository already exists' do
+      let(:path) { project.full_path + '/some/image' }
+
+      it 'returns the existing repository' do
+        container_repository = create(:container_repository, project: project, name: 'some/image')
+
+        expect(repository.id).to eq(container_repository.id)
+      end
+    end
   end
 
   describe '.build_root_repository' do