What is the purpose of the flash map here? The content rendered by the template shows that the flash map is redundant. https://github.com/jooby-project/jooby/blob/6112d76b726e4423ccd85ce703097f464f5d1418/modules/jooby-jte/src/main/java/io/jooby/jte/JteTemplateEngine.java#L41 