The ToolforgeBundle currently accepts any callback query string parameter and uses it for the OAuth initialization. However, if it doesn't match the URL prefix as registered on Meta, errors like the following are thrown:

Uncaught PHP Exception MediaWiki\OAuthClient\Exception: "Server returned error: oauth_callback must be set, and must be set to "oob" (case-sensitive), or the configured callback must be a prefix of the supplied callback." at /mnt/nfs/labstore-secondary-tools-project/svgtranslate/app/vendor/mediawiki/oauthclient/src/Client.php line 148

We could avoid this by adding a new config variable with which to compare the passed callback value, and if the value doesn't match just default to the unsuffixed URL.