Update parser to tap author to set the username to the array key

Normalizes the API

Author: emmadesilva

packages/framework/src/Foundation/Concerns/HasKernelData.php

@@ -50,7 +50,7 @@ public function authors(): Collection
     protected function parseConfigurationAuthors(Collection $authors): Collection
     {
         return $authors->mapWithKeys(function (PostAuthor $author, string $username): array {
-            return [$username ?: $author->username => $author];
+            return [$username => tap($author, fn (PostAuthor $author) => $author->username = $username)];
         });
     }
 }