link the schema resource

lib/api/v3/utilities/path_helper.rb

@@ -104,6 +104,10 @@ module API
             render_markup(format: :textile, link: link)
           end
 
+          def self.schema(project_id, type_id)
+            "#{root}/work_packages/schemas/#{project_id}-#{type_id}"
+          end
+
           def self.statuses
             "#{root}/statuses"
           end

lib/api/v3/work_packages/work_package_representer.rb

@@ -44,6 +44,12 @@ module API
           } if current_user_allowed_to(:edit_work_packages)
         end
 
+        link :schema do
+          {
+            href: api_v3_paths.schema(represented.project.id, represented.type.id)
+          }
+        end
+
         link :updateImmediately do
           {
             href: api_v3_paths.work_package(represented.id),

spec/lib/api/v3/utilities/path_helper_spec.rb

@@ -203,6 +203,16 @@ describe ::API::V3::Utilities::PathHelper do
     end
   end
 
+  describe 'schemas paths' do
+    describe '#schema' do
+      subject { helper.schema 1, 2}
+
+      it_behaves_like 'api v3 path'
+
+      it { is_expected.to match(/^\/api\/v3\/work_packages\/schemas\/1-2/) }
+    end
+  end
+
   describe 'statuses paths' do
     describe '#statuses' do
       subject { helper.statuses }

spec/lib/api/v3/work_packages/work_package_representer_spec.rb

@@ -410,6 +410,16 @@ describe ::API::V3::WorkPackages::WorkPackageRepresenter do
         end
       end
 
+      describe 'schema' do
+        let(:schema_id) { "#{work_package.project.id}-#{work_package.type.id}" }
+        let(:link) { "/api/v3/work_packages/schemas/#{schema_id}".to_json }
+        let(:href_path) { '_links/schema/href' }
+
+        it 'has a link' do
+          is_expected.to be_json_eql(link).at_path(href_path)
+        end
+      end
+
       context 'when the user has the permission to view work packages' do
         context 'and the user is not watching the work package' do
           it 'should have a link to watch' do