Decode a response body as JSON, but keep the rest of the response. Unlike Http.expecJson, you can decode using a Decoder but still get access to response headers, status code, etc.

Complete a request with a predetermined value. Using Json.Decode.succeed fails when the the server doesn't send back valid JSON, as expectJson always attempts to parse the response body as JSON. expectValue skips decoding entirely.

Complete a request with a () value. Skips JSON decoding to always complete with (), regardless of what the server returns.