refactor(postgres): Split postgres module

configuration/default.nix

@@ -1,4 +1,5 @@
 {
+  pkgs,
   lib,
   modulesPath,
   flake-inputs,
@@ -53,6 +54,19 @@
     };
 
     logrotate.enable = true;
+
+    postgresql = {
+      package = pkgs.postgresql_14;
+      enable = true;
+
+      # Only enable connections via the unix socket, and check with the
+      # OS to make sure the user matches the database name.
+      #
+      # See https://www.postgresql.org/docs/current/auth-pg-hba-conf.html
+      authentication = ''
+        local sameuser all peer
+      '';
+    };
   };
 
   security = {