The comment below motivated me to find a better solution for the
repeated authorisation checks:
```php
// This can't be put into a Request authorize(), due to Laravel(?)'s
limitation.
```
This is the result.
The reason being, there might be cases that user have installed but not
configured the module. Auto discovery here will cause the streaming to
fail. With auto discovery removed, Koel will only stream using
mod_xsendfile if MOD_X_SENDFILE_ENABLED env var is found. Hence, users
can disable it in .htaccess if they're not ready.
