Given a req, extract the request query params into a (Map[String, Seq[String]], request).
Given a req, extract the request query params into a (Map[String, Seq[String]], request). The Map is assigned a default value of Nil, so param("p") would return Nil if there is no such parameter, or (as normal for servlets) a single empty string if the parameter was supplied without a value.
Basic query parameter acess.