Refactor GitLab Personal Access Token credential configuration

The token was previously stored as the username, possibly causing authentication failures and exposing the PAT value in log output as a username

Author: codedmonkey

src/Composer/ConfigFactory.php

@@ -69,8 +69,8 @@ private static function buildCredentialsConfig(string $domain, ?Credentials $cre
             CredentialsType::GitlabPersonalAccessToken => [
                 'gitlab-token' => [
                     $domain => [
-                        'username' => $credentials->getToken(),
-                        'token' => 'private-token',
+                        'username' => 'private-token',
+                        'token' => $credentials->getToken(),
                     ],
                 ],
             ],