Add support for `application/octet-stream` content-type responses for async workloads

[RobertLucian]

Description

Currently, only application/json responses are supported for the user's API server. Make it such that we also support application/octet-stream content-type and possibly others too.

[miguelvr]

The response has to be JSON, this is likely never going to change, since the gateway is what responds.

If the user needs a binary format, it should be saved somewhere and return a URL