The JSON-RPC endpoint accepts requests via URL (GET) and JSON (POST). There is
no real point in having client libraries for both modes.
A search of the SDK and on GitHub suggests that most usage is via the JSON
client (via the New constructor) or websocket (NewWS), and the only uses I
found of the NewURI client constructor are in copies of our own test code.
This does not change the functionalitiy of the server, so curl and other
URL-based clients in other languages will still function as before.