WA-230 moving ensureOnce util function to singleton.js

src/utils/singleton.js

@@ -0,0 +1,14 @@
+// @flow
+export const ensureOnce = (fn: Function): Function => {
+  let executed = false
+  let response
+
+  return (...args) => {
+    if (executed) { return response }
+
+    executed = true
+    response = fn(args)
+
+    return response
+  }
+}