Add support for modelPropertyNaming (or similar) to Python codegen.

If you have definitions like this one:

 parameters: - name: FooID in: query 

Then the resulting code uses underscore notation:

 def myendpoint(self, foo_id, ..., **kwargs): # noqa: E501 

It should also be supported to leave the identifiers as-is, so that the code is:

 def myendpoint(self, FooID, ..., **kwargs): # noqa: E501 

Related tickets:

• [Question][Python] Is posible to change to cammel case naming convention? #3813