server challenge for signature authn

request and sign server challenge for authentication
instead of signing url with timestamp
update installer tests

* replace Alpine Linux 3.15 with 3.18
* replace AlmaLinux 8 with 9
* replace Amazon Linux 2022 with 2023
* replace Debian 11 with 12
* replace Fedora 35 with 38
* replace Oracle Linux 8 with 9
* replace Rocky Linux 8 with 9
* add openSUSE 15
* add RHEL 9
* add Ubuntu 22.04 and 23.04
installer script updates

* fix SELinux label for conf files
* check if libsodium can be installed by package manager
  (which it can't on Amazon Linux)
* install Python with packages needed to build PyNaCl wheel
  on Arch Linux, Debian (and derivatives), and Fedora (and derivatives)
* check for broken virtualenv (due to distribution upgrade)
* upgrade pip and setuptools packages in virtualenv
additional systemd service hardening
add python 3.11 to sourcehut build script
explicit support for python 3.11
upgrade prod & lint requirements to latest
update readme with new contributing links
increment year to 2023
updates for flake8 5
sourcehut build manifest to run tox
initial install script
better readme project description
implement file and syslog pipes
basic broker plumbing