nix/modules/knot: make ssh ports configurable

Close: #269
Signed-off-by: Seongmin Lee <[e-mail]>

nix/modules/knot.nix

···
           description = "User that hosts git repos and performs git operations";
         };
 
+        sshPorts = mkOption {
+          type = types.listOf types.port;
+          default = [22];
+          description = "Specifies ports used for ssh";
+        };
+
         openFirewall = mkOption {
           type = types.bool;
           default = true;
-          description = "Open port 22 in the firewall for ssh";
+          description = "Open ssh port in the firewall";
         };
 
         stateDir = mkOption {
···
 
       services.openssh = {
         enable = true;
+        ports = cfg.sshPorts;
         extraConfig = ''
           Match User ${cfg.gitUser}
               AuthorizedKeysCommand /etc/ssh/keyfetch_wrapper
···
         };
       };
 
-      networking.firewall.allowedTCPPorts = mkIf cfg.openFirewall [22];
+      networking.firewall.allowedTCPPorts = mkIf cfg.openFirewall cfg.sshPorts;
     };
   }