Parse the URL leaving the option for the key to be missing (i.e.
Parse the URL leaving the option for the key to be missing (i.e. in the case
that the path for the request is for a finder, or an action, instead of for an individual
element in the collection.)
The url to parse an optional T from.
The parsed result.
Parse the url as if there were nesting / etc.
The url to parse a T from.
Either a ParseSuccess or a ParseFailure.