Move common nix code one level up.

common/consul.nix

@@ -0,0 +1,32 @@
+{ pkgs, config, ... }:
+let
+  servers = [ "c1" "c2" "c3" ];
+  server_enabled = builtins.elem config.networking.hostName servers;
+in
+{
+  services.consul = {
+    enable = true;
+    webUi = true;
+    interface.advertise = "eno1";
+    extraConfig = {
+      client_addr = "0.0.0.0";
+      datacenter = "alo";
+      server = server_enabled;
+      bootstrap_expect = (builtins.length servers + 2) / 2;
+      retry_join = builtins.filter (elem: elem != config.networking.hostName) servers;
+      telemetry = {
+        prometheus_retention_time = "24h";
+        disable_hostname = true;
+      };
+    };
+  };
+
+  environment.persistence."/persist".directories = [
+    "/var/lib/consul"
+  ];
+
+  networking.firewall = {
+    allowedTCPPorts = [ 8600 8500 8301 8302 8300 ];
+    allowedUDPPorts = [ 8600 8301 8302 ];
+  };
+}