Hi,

Using home-openssh-service-type on Ubuntu 22.10 (OpenSSH_9.3p1, OpenSSL
1.1.1t 7 Feb 2023) always creates an ~/.ssh/authorized_keys that breaks
key-based login.  I cannot access the logs and don't know what the
problem might be.

When, after running `guix home reconfigure', you do something like:

--8<---------------cut here---------------start------------->8---
mv .ssh/authorized_keys .ssh/authorized_keys-
cat .ssh/authorized_keys- > .ssh/authorized_keys
chmod 400 .ssh/authorized_keys
--8<---------------cut here---------------end--------------->8---
    
key-based login succeeds.

A workaround would be to have home-openssh-service-type leave
~/.ssh/authorized_keys alone.  However, when using

--8<---------------cut here---------------start------------->8---
(service
  home-openssh-service-type
  (home-openssh-configuration
   (authorized-keys '())))
--8<---------------cut here---------------end--------------->8---

any existing ~/.ssh/authorized_keys file is removed and replaced by a
symlink to an empty file.  I don't see how that is useful, it certainly
breaks key-based login.

Using

--8<---------------cut here---------------start------------->8---
(service
  home-openssh-service-type
  (home-openssh-configuration
   (authorized-keys #f)))
--8<---------------cut here---------------end--------------->8---

yields a backtrace.

The attached patch fixes that and allows using (authorized-keys #f),
also making this the default.

WDYT?

Greetings,
Janneke