[REQ][Java][Client] add support for `text/csv` content

[aaronforest-wf]

Is your feature request related to a problem? Please describe.

Java client does not support text/csv (or any text/* content types besides text/plain)

Describe the solution you'd like

It seems like this check could be loosened so that any text/* mime type response would be returned as a String

Describe alternatives you've considered

Allowing custom mappers to be configured from mime types to specific classes may be useful.

Additional context

The error I currently hit when using a generated java client to get text/csv content is something like this:

Deserialization for content type 'text/csv' not supported for type '...@...'
ApiException{code=200, responseHeaders={...}, responseBody='...'}