Display maximum artifact size from runtime config

The maximum artifact size was moved into runtime config some time ago.
Update the instance configuration code to read this value.

app/models/instance_configuration.rb

@@ -39,7 +39,7 @@ class InstanceConfiguration
   def gitlab_ci
     Settings.gitlab_ci
             .to_h
-            .merge(artifacts_max_size: { value: Settings.artifacts.max_size&.megabytes,
+            .merge(artifacts_max_size: { value: Gitlab::CurrentSettings.max_artifacts_size.megabytes,
                                          default: 100.megabytes })
   end
 

changelogs/unreleased/instance-configuration-artifact-size.yml

+---
+title: Display maximum artifact size from runtime config
+merge_request: 26784
+author: Bastian Blank
+type: fixed

spec/models/instance_configuration_spec.rb

@@ -82,6 +82,13 @@ describe InstanceConfiguration do
         it 'returns the key artifacts_max_size' do
           expect(gitlab_ci.keys).to include(:artifacts_max_size)
         end
+
+        it 'returns the key artifacts_max_size with values' do
+          stub_application_setting(max_artifacts_size: 200)
+
+          expect(gitlab_ci[:artifacts_max_size][:default]).to eq(100.megabytes)
+          expect(gitlab_ci[:artifacts_max_size][:value]).to eq(200.megabytes)
+        end
       end
     end
   end