Resolves the body into a bytestring.
Resolves the body into a bytestring. This operation completes immediately for static responses. For streaming responses, this only completes when all data has been received. Be aware if the response is an infinite stream of data (using chunked transfer encoding), this will never complete.
Be aware, at the moment when the response is encoded, there is no processing on the response body, and no headers are added in. This means if the transfer-encoding is "chunked", the header must already exist and the stream must already be prepending chunk headers to the data.