fix(postgres): create .first_startup file after initdb

This file is used by the postgresql-setup script to determine if it's the first time the database is being started.

Author: jfroche

nix/systemModules/postgres/default.nix

@@ -315,6 +315,10 @@ in
  # Initialise the database.
  initdb ${lib.escapeShellArgs cfg.initdbArgs}
  fi
+
+ # See postgresql-setup
+ touch "${cfg.dataDir}/.first_startup"
+
  if [ ! -f /etc/postgresql-custom/pgsodium_root.key ]; then
  umask 077
  echo "0000000000000000000000000000000000000000000000000000000000000000" > /etc/postgresql-custom/pgsodium_root.key