Start reworking the server for nix flakes

This removes all existing services as well, in preparation of moving
them to `podman`. These are easier to update to
virtualisation.oci-containers while retaining the "networks" through
pods.

README.md

@@ -6,51 +6,30 @@ This is the NixOS configuration for [tlater.net](https://tlater.net/).
 
 ### Building
 
-To test locally in a VM, [nix](https://nixos.org/nix/) is
-required. Using a properly-configured nix, a qemu-based VM running the
-server can be created by first applying the following patch to disable
-hardware-specific configuration:
-
-```patch
-diff --git a/etc/nixos/configuration.nix b/etc/nixos/configuration.nix
-index 387113d..aabee88 100644
---- a/etc/nixos/configuration.nix
-+++ b/etc/nixos/configuration.nix
-@@ -2,8 +2,8 @@
-
- {
-   imports = [
--    ./hardware-configuration.nix
--    ./linode.nix
-+    # ./hardware-configuration.nix
-+    # ./linode.nix
-   ];
-
-   networking = {
-```
-
-Then building the VM with:
+Build the VM with:
 
 ```
-nix-build '<nixpkgs/nixos>' -A vm -k -I nixos-config=./configuration.nix
+nixos-rebuild build-vm --flake '.#vm'
 ```
 
 ### Running
 
-To invoke the VM, use:
+Running should *mostly* be as simple as running the command the build
+script echos.
 
-```
-QEMU_NET_OPTS="hostfwd=tcp::2222-:2222,hostfwd=tcp::8000-:80" ./result/bin/run-tlater.net-vm
+One caveat: create a larger disk image first. This can be done by
+running the following in the repository root:
+
+```bash
+qemu-img create -f qcow2 ./tlaternet.qcow2 20G
 ```
 
-This will set up a qemu VM with ports 2222 linked to the ssh port, and
-8000 to the http port. If other ports are required, adjust the
-environment variable (notably, ssl is provided by the image, although
-it should not work since it is unlikely that letsencrypt will supply
-any certificates).
+Everything else should be handled by the devShell.
 
-Note that other environment variables are available (such as one for
-disabling the qt GUI, probably handy for eventual CI). They are listed
-under "Building a service as a VM (for testing)"
-[here](https://nixos.wiki/wiki/Cheatsheet) (not linked since the page
-isn't set up very nicely).
+### New services
+
+Whenever a new service is added, append an appropriate
+`,hostfwd=::3<port>:<port>` to the `QEMU_NET_OPTS` specified in
+`flake.nix` to bind the service to a host port.
+
+There is no way to test this without binding to the host port, sadly.