Ignore $remote-user if --ssh-user or SSHUSER was set

[VeloAddict]

I have configured the container with a specific user using SSHUSER env, and I only want that user to ssh into the server.
I am also running wetty behind nginx proxy manager with authentication provided by authelia and $remote-user is passed along in the headers. This sets the user for the ssh connection to an user that does not exist or does not have a shell.

It would be great if wetty ignored $remote-user header when and the env SSHUSER is set.