Swap metrics_dashboard to use metric_id and env_id

ee/app/controllers/projects/prometheus/alerts_controller.rb

@@ -14,7 +14,7 @@ module Projects
       prepend_before_action :repository, :project_without_auth, only: [:notify]
 
       before_action :authorize_read_prometheus_alerts!, except: [:notify]
-      before_action :alert, only: [:update, :show, :destroy]
+      before_action :alert, only: [:update, :show, :destroy, :metrics_dashboard]
 
       def index
         render json: serialize_as_json(alerts)
@@ -140,7 +140,7 @@ module Projects
       def metrics_dashboard_params
         {
           embedded: true,
-          prometheus_alert_id: params[:id].to_i
+          prometheus_alert_id: alert.id
         }
       end
     end

ee/spec/controllers/projects/prometheus/alerts_controller_spec.rb

@@ -364,19 +364,33 @@ describe Projects::Prometheus::AlertsController do
     end
 
     it 'returns a json object with the correct keys' do
-      get :metrics_dashboard, params: request_params(id: alert.id), format: :json
+      get :metrics_dashboard, params: request_params(id: metric.id, environment_id: alert.environment.id), format: :json
 
       expect(response).to have_gitlab_http_status(:ok)
       expect(json_response.keys).to contain_exactly('dashboard', 'status')
     end
 
     it 'is the correct embed' do
-      get :metrics_dashboard, params: request_params(id: alert.id), format: :json
+      get :metrics_dashboard, params: request_params(id: metric.id, environment_id: alert.environment.id), format: :json
 
       title = json_response['dashboard']['panel_groups'][0]['panels'][0]['title']
 
       expect(title).to eq(metric.title)
     end
+
+    it 'finds the first alert embed without environment_id' do
+      get :metrics_dashboard, params: request_params(id: metric.id), format: :json
+
+      title = json_response['dashboard']['panel_groups'][0]['panels'][0]['title']
+
+      expect(title).to eq(metric.title)
+    end
+
+    it 'returns 404 for non-existant alerts' do
+      get :metrics_dashboard, params: request_params(id: 0), format: :json
+
+      expect(response).to have_gitlab_http_status(:not_found)
+    end
   end
 
   def project_params(opts = {})