feat(ssh/openssh): overhauling ssh and openssh modules

modules/nixos/services/openssh/default.nix

@@ -1,19 +1,43 @@
 {
   config,
+  outputs,
   lib,
+  self,
   ...
 }:
 let
+  hosts = lib.attrNames outputs.nixosConfigurations;
   inherit (lib) mkIf mkEnableOption;
   cfg = config.nixos.services.openssh;
+
+  hostsWithKeys = builtins.filter (
+    hostname: builtins.pathExists "${self}/hosts/${hostname}/ssh_host_ed25519_key.pub"
+  ) hosts;
 in
 {
   options = {
-    nixos.services.openssh.enable = mkEnableOption "Enables openssh";
+    nixos.services.openssh = {
+      enable = mkEnableOption "Enables openssh";
+    };
   };
+
   config = mkIf cfg.enable {
+    programs.ssh = {
+      knownHosts = lib.genAttrs hostsWithKeys (hostname: {
+        publicKeyFile = "${self}/hosts/${hostname}/ssh_host_ed25519_key.pub";
+      });
+    };
+
     services.openssh = {
       enable = true;
+      settings = {
+        AcceptEnv = "WAYLAND_DISPLAY";
+        GatewayPorts = "clientspecified";
+        PasswordAuthentication = false;
+        PermitRootLogin = "no";
+        StreamLocalBindUnlink = "yes";
+        X11Forwarding = true;
+      };
     };
   };
 }