Get dir path for page convert [core, blog!] to "./core/pages/blog" convert [ext, blog!] to "./ext/pages/ext_blog" convert [core, foo.bar] to "./core/pages/foo/foo_bar" convert [ext, foo.bar] to "./ext/pages/foo/ext_foo_bar" convert [core, home] to "./core/pages/home_page" convert [ext, home] to "./ext/pages/ext_home_page".

Get pkg name for page convert [core, blog!] to "blog" convert [ext, blog!] to "ext_blog" convert [core, foo.bar] to "foo_bar" convert [ext, foo.bar] to "ext_foo_bar" convert [core, home] to "home_page" convert [ext, home] to "ext_home_page".

PathPrefix returns the path for an app, regarding the env variable `WATERWAY_MULTI_APP` if WATERWAY_MULTI_APP is "1", then call this function with "blog" will return "/blog", otherwise it returns empty path.