Record user that erased a build through API

lib/api/builds.rb

@@ -138,7 +138,7 @@ module API
         return not_found!(build) unless build
         return forbidden!('Build is not erasable!') unless build.erasable?
 
-        build.erase
+        build.erase(erased_by: current_user)
         present build, with: Entities::Build,
                        user_can_download_artifacts: can?(current_user, :download_build_artifacts, user_project)
       end

spec/requests/api/builds_spec.rb

@@ -184,6 +184,11 @@ describe API::API, api: true  do
         expect(build.artifacts_file.exists?).to be_falsy
         expect(build.artifacts_metadata.exists?).to be_falsy
       end
+
+      it 'should update build' do
+        expect(build.reload.erased_at).to be_truthy
+        expect(build.reload.erased_by).to eq user
+      end
     end
 
     context 'build is not erasable' do