Enhance webauthn error handling at registration

resources/js/webauthn/isValidDomain.js

@@ -0,0 +1,15 @@
+/**
+ * A simple test to determine if a hostname is a properly-formatted domain name
+ *
+ * A "valid domain" is defined here: https://url.spec.whatwg.org/#valid-domain
+ *
+ * Regex sourced from here:
+ * https://www.oreilly.com/library/view/regular-expressions-cookbook/9781449327453/ch08s15.html
+ */
+export function isValidDomain(hostname) {
+    return (
+        // Consider localhost valid as well since it's okay wrt Secure Contexts
+        hostname === 'localhost' ||
+        /^([a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}$/i.test(hostname)
+    );
+}