docs: add sections and fix typos/errors

few side refactors of this:
- no more `dns.domain`, it all must rely on `fqdn`, prevents
  inconsistencies.
- also added an specific host `tuxcord-acmetest` that uses the key zone
  for `nix.tuxcord.net` to test certificate pulling.

nixos/openssh.nix

@@ -10,6 +10,14 @@
       PermitRootLogin = "no";
     };
   };
+<<<<<<< HEAD
 
   networking.firewall.allowedTCPPorts = [ 22 ];
+||||||| parent of 1c2f11d (lib/ssh: add more ssh keys)
+
+  users.users.root.openssh.authorizedKeys.keys = builtins.attrValues {
+    inherit (import "${self}/lib/ssh/keys.nix") error javalsai;
+  };
+=======
+>>>>>>> 1c2f11d (lib/ssh: add more ssh keys)
 }

nixos/vm.nix

@@ -7,8 +7,8 @@
     memorySize = 4096;
 
     qemu.networkingOptions = lib.mkForce [
-      "-net nic,netdev=user.0,model=virtio"
-      "-netdev user,id=user.0,\${QEMU_NET_OPTS:+,$QEMU_NET_OPTS}"
+      "-nic bridge,br=virbr0,id=hn0,model=virt-net-pci,helper=\${QEMU_BRIDGE_HELPER_PATH}"
+      "-device virtio-net-pci,netdev=hn0,id=nic1,\${QEMU_NET_OPTS:+,$QEMU_NET_OPTS}"
     ];
   };
 }

shells/default.nix

@@ -5,6 +5,24 @@
     {
       devShells.default = pkgs.mkShell {
         name = "configuration.nix";
+
+        shellHook = ''
+          for path in \
+            /usr/lib/qemu/qemu-bridge-helper \
+            /run/wrappers/bin/qemu-bridge-helper
+          do
+            if [ -x "$path" ]; then
+              export QEMU_BRIDGE_HELPER_PATH="$path"
+              break
+            fi
+          done
+
+          if [ -z "$QEMU_BRIDGE_HELPER_PATH" ]; then
+            printf "\033[1;33m%s\033[0m\n" \
+              "WARN: 'qemu-bridge-helper' not found, make sure it is installed and the nix shell hook is looking for it" >&2
+          fi
+        '';
+
         packages = with pkgs; [
           bat
           cachix