Add a health action to sites controller to check g5k-api availability

Fixes: bug #13404

app/controllers/sites_controller.rb

@@ -135,6 +135,11 @@ class SitesController < ResourcesController
     render_result(result)
   end
 
+  # Healthcheck of g5k-api, used to check if the app is running.
+  def health
+    render json: { status: 'OK' }
+  end
+
   protected
 
   def collection_path

config/routes.rb

@@ -52,6 +52,7 @@ Api::Application.routes.draw do
 
     member do
       get :status
+      get :health
     end
 
     resources :network_equipments, only: %i[index show]

spec/controllers/sites_controller_spec.rb

@@ -265,4 +265,13 @@ describe SitesController do
       expect(json['version']).to eq 'f449f0cb61b0cf5adf1ddbae47c9a409af9652f1'
     end
   end
+
+  describe 'GET /sites/{{id}}/health' do
+    it 'should get a 200 with a simple JSON' do
+      get :health, params: { id: 'rennes' }, format: :json
+      expect(response.status).to eq 200
+      expect(json.length).to eq 1
+      expect(json['status']).to eq 'OK'
+    end
+  end
 end