* segments `["a", "b"]` build "/a/b" and the segments `["a", "b", ""]` build "/a/b/".
 *
 * If a path's last segment is the empty string then the path ends with "/". This class always
 * builds non-empty paths: if the path is omitted it defaults to "/". The default path's segment
 * list is a single empty string: `[""]`.
 *
 * ### Query
 *
 * The query is optional: it can be null, empty, or non-empty. For many HTTP URLs the query string