Clz_cohttpSourcedecompress (resp, body) returns the contents of body, decompressed using the information from the "content-encoding" header or fails with ClzError msg if there are decompression issues or an unknown algorithm is required.
update_header h returns a new header including "accept-encoding: gzip,deflate" if h=None or force=true. When force=false (default) it adds the header only if was not already present.