Cleanup duplicates in deploymentEntityDetailed and add small spec tests

app/serializers/deployment_entity_detailed.rb

-class DeploymentEntityDetailed < Grape::Entity
-  include RequestAwareEntity
-
-  expose :id
-  expose :iid
-  expose :sha
-
+class DeploymentEntityDetailed < DeploymentEntity
   expose :ref do
-    expose :name do |deployment|
-      deployment.ref
-    end
-
     expose :ref_path do |deployment|
       namespace_project_tree_path(
         deployment.project.namespace,
@@ -18,9 +8,6 @@ class DeploymentEntityDetailed < Grape::Entity
     end
   end
 
-  expose :created_at
-  expose :tag
-  expose :last?
   expose :user, using: UserEntity
   expose :commit, using: CommitEntity
   expose :deployable, using: BuildEntity

spec/serializers/deployment_entity_detailed_spec.rb

+require 'spec_helper'
+
+describe DeploymentEntityDetailed do
+  let(:user) { create(:user) }
+  let(:request) { double('request') }
+  let(:deployment) { create(:deployment) }
+  let(:entity) { described_class.new(deployment, request: request) }
+  subject { entity.as_json }
+
+  before do
+    allow(request).to receive(:user).and_return(user)
+  end
+
+  it 'exposes internal deployment id'  do
+    expect(subject).to include(:iid)
+  end
+
+  it 'exposes nested information about branch' do
+    expect(subject[:ref][:name]).to eq 'master'
+    expect(subject[:ref][:ref_path]).not_to be_empty
+  end
+
+  it 'exposes creation date' do
+    expect(subject).to include(:created_at)
+  end
+end

spec/serializers/deployment_entity_spec.rb

 require 'spec_helper'
 
-describe DeploymentEntityDetailed do
+describe DeploymentEntity do
   let(:user) { create(:user) }
   let(:request) { double('request') }
+  let(:deployment) { create(:deployment) }
+  let(:entity) { described_class.new(deployment, request: request) }
+  subject { entity.as_json }
 
   before do
     allow(request).to receive(:user).and_return(user)
   end
 
-  let(:entity) do
-    described_class.new(deployment, request: request)
-  end
-
-  let(:deployment) { create(:deployment) }
-
-  subject { entity.as_json }
-
   it 'exposes internal deployment id'  do
     expect(subject).to include(:iid)
   end
 
   it 'exposes nested information about branch' do
     expect(subject[:ref][:name]).to eq 'master'
-    expect(subject[:ref][:ref_path]).not_to be_empty
   end
 
   it 'exposes creation date' do