add api call - get mock url next

app/assets/javascripts/vue_pipelines_index/stage.js.es6

-/* global Vue, gl */
+/* global Vue, Flash, gl */
 /* eslint-disable no-param-reassign */
 
 ((gl) => {
@@ -23,6 +23,17 @@
       spanClass() {
         return `ci-status-icon ci-status-icon-${this.stage.status.group}`;
       },
+      methods: {
+        fetchBuilds() {
+          this.$http.get(this.stage.status.endpoint)
+            .then((response) => {
+              Vue.set(this, 'builds', response.html);
+              Vue.set(this, 'response', true);
+            }, () => new Flash(
+              'Something went wrong on our end.',
+            ));
+        },
+      },
     },
     template: `
       <div class="stage-container mini-pipeline-graph">