Fix isInternalUrl for subdomain support

Refactor / reduce plumbing

app/utils/isInternalUrl.js

@@ -1,12 +1,19 @@
 // @flow
+import parseDomain from 'parse-domain';
+
 export default function isInternalUrl(href: string) {
   if (href[0] === '/') return true;
 
-  try {
-    const outline = new URL(BASE_URL);
-    const parsed = new URL(href);
-    return parsed.hostname === outline.hostname;
-  } catch (err) {
-    return false;
+  const outline = parseDomain(BASE_URL);
+  const parsed = parseDomain(href);
+  if (
+    parsed &&
+    outline &&
+    parsed.domain === outline.domain &&
+    parsed.tld === outline.tld
+  ) {
+    return true;
   }
+
+  return false;
 }