feat(modules/dgn-console): Add a pg upgrade script when necessary

modules/dgn-console.nix

@@ -1,13 +1,18 @@
 { config, lib, pkgs, ... }:
 
 let
-  inherit (lib) mkEnableOption mkIf;
+  inherit (lib) mkEnableOption mkOption mkIf;
 
   cfg = config.dgn-console;
 
 in {
   options.dgn-console = {
     enable = mkEnableOption "DGNum console setup." // { default = true; };
+
+    pg-upgrade-to = mkOption {
+      type = lib.types.package;
+      default = pkgs.postgresql_15;
+    };
   };
 
   config = mkIf cfg.enable {
@@ -15,8 +20,6 @@ in {
 
     console = { keyMap = "fr"; };
 
-    environment.systemPackages = with pkgs; [ neovim wget kitty.terminfo ];
-
     environment.variables.EDITOR = "nvim";
 
     programs.neovim.vimAlias = true;
@@ -58,5 +61,30 @@ in {
     '';
 
     hardware.enableRedistributableFirmware = true;
+
+    environment.systemPackages = (with pkgs; [ neovim wget kitty.terminfo ])
+      ++ lib.optional (config.services.postgresql.package != cfg.pg-upgrade-to)
+      (pkgs.writeScriptBin "upgrade-pg-cluster" ''
+        set -eux
+        # XXX it's perhaps advisable to stop all services that depend on postgresql
+        systemctl stop postgresql
+
+        export NEWDATA="/var/lib/postgresql/${cfg.pg-upgrade-to.psqlSchema}"
+
+        export NEWBIN="${cfg.pg-upgrade-to}/bin"
+
+        export OLDDATA="${config.services.postgresql.dataDir}"
+        export OLDBIN="${config.services.postgresql.package}/bin"
+
+        install -d -m 0700 -o postgres -g postgres "$NEWDATA"
+        cd "$NEWDATA"
+        sudo -u postgres $NEWBIN/initdb -D "$NEWDATA"
+
+        sudo -u postgres $NEWBIN/pg_upgrade \
+          --old-datadir "$OLDDATA" --new-datadir "$NEWDATA" \
+          --old-bindir $OLDBIN --new-bindir $NEWBIN \
+          "$@"
+      '');
+
   };
 }