Support alternative Mime-types other than application/json

[medcelerate]

Is your feature request related to a problem? Please describe.
Currently all endpoints default to application/json without the ability to change the expected return type. The workaround we have currently is by including the Content-Type response header but it would be better to define a different produces call.

Describe the solution you'd like
We would like to be able to pass into a response object a field similar to {@content contentType: "application/octect-strean"}

Describe alternatives you've considered
We would also accept a way to do this with jsDoc but the first option would be better.

[lfportal]

See #1150 for a similar issue