Allow the user to pass in any headers per request.
Created by: Amelia0193
Is your feature request related to a problem? Please describe.
User cannot pass a header parameter different from the ones in all_params to the request level.
Describe the solution you'd like
The header_params will be updated to get all the headers the users passed in, if none is defaulting to {}.
Describe alternatives you've considered
Specify the header needed in the all_params and append it to the header_params. But you need to do that for all the parameters the user want to support. The above solution is a more generic one which I think simplifies and helps for the future.