[REQ] Client:Python Add default parameters to function definition

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

The original API declares a parameter with a default value. This value does not
show as default value in the python function definition. As a consequence I get less than optional IDE support for my functions and need to retype the value.

Describe the solution you'd like

If the openapi defnition contains a default field in the parameter schema section I would like it to be encoded in the python function header. e.g.
fun call_some_api_using_post(self, param=/default/, **kwargs):

Describe alternatives you've considered

1. Server side modification
   I could make that parameter optionional and fill in the parameter on the server side if it is missing. This solution is frustrating, because there is little IDE support for it. I want automatic parameter completion (intellisense) and automated lists of available parameters.

2. Including all optional parameters
   All optional parameters could be included in the python header with default None, e.g.
   fun call_some_api_using_post(self, optional_param1=None, optional_param2=None, **kwargs):

I rejected this solution because it would be more invasive and generate code that would be redundant for use cases that do not aim for optimized editor support.

Additional context

If such a feature is welcome I would work on a pull request. I was trying to follow the guidelines form the README in this project.

The issue names no files or tests; begin by locating the Python client generator's parameter-schema handling and its generated function-signature tests. Done means an OpenAPI parameter default is emitted in the generated Python function definition without adding unrelated optional parameters, with coverage for the requested behavior.