config: restructure config tree and file names:

```
config/
|- services/
|- |- <service-name>.nix
```

.gitignore

@@ -0,0 +1 @@
+secrets/

config/net.nix

@@ -18,7 +18,7 @@
   # DOCS: https://nixos.wiki/wiki/WireGuard
   networking.wireguard.enable = true;
   networking.wireguard.interfaces.wg0 = {
-    privateKeyFile = "/etc/nixos/wireguard.private";
+    privateKeyFile = "/etc/nixos/secrets/wireguard.private";
     # wg is active only in this namespace.
     # run e.g. ip netns ovpns <some command like ping/curl/etc, it'll go through wg>
     # note: without the namespace, you'll need to add a specific route through eth0 for the peer (185.157.162.7/32)

config/services/pleroma.nix

@@ -6,7 +6,7 @@
 {
   services.pleroma.enable = true;
   # XXX colin: this isn't checked into git, so make sure to create it first:
-  services.pleroma.secretConfigFile = "/etc/nixos/services-conf/pleroma.secret.exs";
+  services.pleroma.secretConfigFile = "/etc/nixos/secrets/pleroma.secret.exs";
   # services.pleroma.secretConfigFile = "/var/lib/pleroma/prod.secret.exs";
   services.pleroma.configs = [
     ''

configuration.nix

@@ -7,19 +7,19 @@
 {
   imports =
     [ # Include the results of the hardware scan.
-      ./fs-configuration.nix
-      ./hardware-configuration.nix
-      ./net-configuration.nix
-      ./services-conf/gitea-configuration.nix
-      ./services-conf/jackett-configuration.nix
-      ./services-conf/jellyfin-configuration.nix
-      ./services-conf/matrix-configuration.nix
-      ./services-conf/nginx-configuration.nix
-      ./services-conf/pleroma-configuration.nix
-      ./services-conf/postfix-configuration.nix
-      ./services-conf/postgres-configuration.nix
-      ./services-conf/transmission-configuration.nix
-      ./user-configuration.nix
+      ./config/fs.nix
+      ./config/hardware.nix
+      ./config/net.nix
+      ./config/users.nix
+      ./config/services/gitea.nix
+      ./config/services/jackett.nix
+      ./config/services/jellyfin.nix
+      ./config/services/matrix.nix
+      ./config/services/nginx.nix
+      ./config/services/pleroma.nix
+      ./config/services/postfix.nix
+      ./config/services/postgres.nix
+      ./config/services/transmission.nix
     ];
 
   nixpkgs.overlays = [