Would like to know  if "Accept" and "Content-Type" is mandatory for all  APIs ? If yes, then will the following be considered as valid "Content-Type" for CDR perspective 

"application/octet-stream" 

In similar lines will "audio/basic" be considered valid in "Accept" header ?

Similarly in "https://consumerdatastandardsaustralia.github.io/standards/#http-headers" example i see "Accept-Encoding" as well , is that an additional header?