Ui/pricing metrics params (#10083)

metrics route takes start and end params and passes to the date display field, as well as the route's API call

ui/app/helpers/parse-date-string.js

@@ -0,0 +1,20 @@
+import { helper } from '@ember/component/helper';
+import { isValid } from 'date-fns';
+
+export function parseDateString(date, separator = '-') {
+  // Expects format MM-YYYY by default: no dates
+  let datePieces = date.split(separator);
+  if (datePieces.length === 2) {
+    if (datePieces[0] < 1 || datePieces[0] > 12) {
+      throw new Error('Not a valid month value');
+    }
+    let firstOfMonth = new Date(datePieces[1], datePieces[0] - 1, 1);
+    if (isValid(firstOfMonth)) {
+      return firstOfMonth;
+    }
+  }
+  // what to return if not valid?
+  throw new Error(`Please use format MM${separator}YYYY`);
+}
+
+export default helper(parseDateString);