add init

lib.nix

@@ -108,6 +108,13 @@ in
           )
         );
       };
+      setupInitialDatabases = if initialDatabases != [] then (
+        lib.concatMapStrings (db: ''
+        echo "Checking presence of database ${db.name}"
+        dbAlreadyExists="$(echo "SELECT 1 AS result FROM pg_database WHERE datname='${db.name}';" | psql --dbname postgres | ${pkgs.gnugrep}/bin/grep -c 'exists = "1"' || true)"
+        echo $dbAlreadyExists
+        '') initialDatabases
+        );
       setupScript = pkgs.writeShellApplication {
         name = "setup-postgres";
         runtimeInputs = [
@@ -129,6 +136,7 @@ in
             echo "PostgreSQL is setting up the initial database"
             echo
             pg_ctl -w start -o "-c listen_addresses= -p ${builtins.toString port}"
+            ${setupInitialDatabases}
             pg_ctl -m fast -w stop
           else 
             echo