Use this endpoint for accessing a single listing. When you
make a search to the /properties endpoint, each listing in
the response will contain a unique mlsId field which should
be used to request that listing on this route.
The mlsId field is a unique identifier for a listing which
is specific to the SimplyRETS API only. It is different from
the listingId field is the public number given to a listing
by the MLS and is not used here.