Attempt to fetch data from a contract data map. The contract is identified with [Stacks Address] and [Contract Name] in the URL path. The map is identified with [Map Name].
The key to lookup in the map is supplied via the POST body. This should be supplied as the hex string serialization of the key (which should be a Clarity value). Note, this is a JSON string atom.
In the response, data is the hex serialization of the map response. Note that map responses are Clarity option types, for non-existent values, this is a serialized none, and for all other responses, it is a serialized (some ...) object.