Features:
+* add new "systemd-ssh-generator", which allows basic ssh config via
+ credentials (host key). It generates sshd.socket for IP, but also
+ sshd-vsock.socket for listening on AF_VSOCK when running in a VM, and
+ sshd-unix.socket on AF_UNIX when running in a container. It also generates a
+ matching sshd.service file with a host key passed in on the cmdline via
+ credentials. Then, add a ssh_config drop-in that matches some suitable
+ hostname pattern and has a ProxyCommand set that allows connecting to any
+ local VM/container that way without any networking configured.
+
* in the service manager, pick up ERRNO= + BUSERROR= + VARLINKERROR= error
identifiers, and store them along with the exit status of a server and report
via "systemctl status".