PostgreSQLDialect support to unparse LISTAGG aggregate function

@Test void testPostgresqlLISTAGG() {
  final String query = "SELECT \"product_class_id\","
      + "LISTAGG(DISTINCT CAST(\"brand_name\" AS VARCHAR), ',') "
      + "FROM \"foodmart\".\"product\" group by \"product_class_id\"";
  sql(query).withPostgresql().ok("SELECT \"product_class_id\", LISTAGG(DISTINCT CAST(\"brand_name\" AS VARCHAR), ',')\n"
      + "FROM \"foodmart\".\"product\"\nGROUP BY \"product_class_id\"");
} 

SELECT  "sex",  LISTAGG(DISTINCT CAST("patient"."id" AS VARCHAR), ',') AS "list"FROM  "patient"GROUP BY  "sex"