Add code_navigation_references feature flag

We are adding support to find references via Code Intelligence.

This adds the `code_navigation_references` feature flag which will
be used to determine whether `ProcessLsifReferences` header will
be `true` or `false`.

If it's `true` then gitlab-workhorse will be parsing the LSIF
with references.

app/services/ci/create_job_artifacts_service.rb

@@ -22,7 +22,11 @@ module Ci
       return result unless result[:status] == :success
 
       headers = JobArtifactUploader.workhorse_authorize(has_length: false, maximum_size: max_size(artifact_type))
-      headers[:ProcessLsif] = true if lsif?(artifact_type)
+
+      if lsif?(artifact_type)
+        headers[:ProcessLsif] = true
+        headers[:ProcessLsifReferences] = Feature.enabled?(:code_navigation_references, project, default_enabled: false)
+      end
 
       success(headers: headers)
     end

spec/requests/api/ci/runner_spec.rb

@@ -1823,13 +1823,36 @@ RSpec.describe API::Ci::Runner, :clean_gitlab_redis_shared_state do
             expect(json_response['ProcessLsif']).to be_truthy
           end
 
+          it 'adds ProcessLsifReferences header' do
+            authorize_artifacts_with_token_in_headers(artifact_type: :lsif)
+
+            expect(response).to have_gitlab_http_status(:ok)
+            expect(json_response['ProcessLsifReferences']).to be_truthy
+          end
+
           context 'code_navigation feature flag is disabled' do
-            it 'does not add ProcessLsif header' do
+            it 'responds with a forbidden error' do
               stub_feature_flags(code_navigation: false)
+              authorize_artifacts_with_token_in_headers(artifact_type: :lsif)
+
+              aggregate_failures do
+                expect(response).to have_gitlab_http_status(:forbidden)
+                expect(json_response['ProcessLsif']).to be_falsy
+                expect(json_response['ProcessLsifReferences']).to be_falsy
+              end
+            end
+          end
 
+          context 'code_navigation_references feature flag is disabled' do
+            it 'sets ProcessLsifReferences header to false' do
+              stub_feature_flags(code_navigation_references: false)
               authorize_artifacts_with_token_in_headers(artifact_type: :lsif)
 
-              expect(response).to have_gitlab_http_status(:forbidden)
+              aggregate_failures do
+                expect(response).to have_gitlab_http_status(:ok)
+                expect(json_response['ProcessLsif']).to be_truthy
+                expect(json_response['ProcessLsifReferences']).to be_falsy
+              end
             end
           end
         end