Request headers missing when using :open_api

[felixletkemann]

In case I use :html or :json or :markdown as config.format option, I always see the request headers "Authorization" and "Content-Type" in the document. As soon as I select open_api, there are just the response headers in the rendered YAML file.
When I put a debug point (binding.pry) in lib/rspec_api_documentation/writers/open_api_writer.rb -> requests method, I can clearly see, that these headers are there. Somehow they get lost afterwards.
So far, I have not been able to find out where this gets lost. In case I find out, I will post the solution here.