Add icon field to instance endpoint (#30205)

spec/helpers/instance_helper_spec.rb

@@ -24,4 +24,33 @@ describe InstanceHelper do
       expect(helper.site_hostname).to eq 'example.com'
     end
   end
+
+  describe 'favicon' do
+    context 'when an icon exists' do
+      let!(:favicon) { Fabricate(:site_upload, var: 'favicon') }
+      let!(:app_icon) { Fabricate(:site_upload, var: 'app_icon') }
+
+      it 'returns the URL of the icon' do
+        expect(helper.favicon_path).to eq(favicon.file.url('48'))
+        expect(helper.app_icon_path).to eq(app_icon.file.url('48'))
+      end
+
+      it 'returns the URL of the icon with size parameter' do
+        expect(helper.favicon_path(16)).to eq(favicon.file.url('16'))
+        expect(helper.app_icon_path(16)).to eq(app_icon.file.url('16'))
+      end
+    end
+
+    context 'when an icon does not exist' do
+      it 'returns nil' do
+        expect(helper.favicon_path).to be_nil
+        expect(helper.app_icon_path).to be_nil
+      end
+
+      it 'returns nil with size parameter' do
+        expect(helper.favicon_path(16)).to be_nil
+        expect(helper.app_icon_path(16)).to be_nil
+      end
+    end
+  end
 end