[python-flask] stub not called if requiered parameters in header

Description

The stub are not called if there is requiered parameters in header

      parameters:
      - name: "api_version"
        in: "header"
        required: true
        type: "integer"
        enum:
        - 1
        - 2
        - 3
      - in: "body"
        name: "body"
        description: "Pet object that needs to be added to the store"
        required: true
        schema:
          $ref: "#/definitions/Pet"

cf. controller.mustache, if parameter in header is "required: true" :

template :

...
def {{operationId}}({{#allParams}}{{paramName}}{{^required}}=None{{/required}}{{#hasMore}}, {{/hasMore}}{{/allParams}}):  # noqa: E501
    """{{#summary}}{{.}}{{/summary}}{{^summary}}{{operationId}}{{/summary}}
...

generated code :

def add_pet(api_version, body):  # noqa: E501

But it seems that the {{^required}}=None{{/required}} is incompatible with the current connection framework on top of Flask.
"Currently, header parameters are not passed to the handler functions as parameters. But they can be accessed through the underlying connexion.request.headers object which aliases the flask.request.headers object."

Temporarly to be defined

def add_pet(api_version=None, body=None):  # noqa: E501

Swagger-codegen version

2.4.23

Swagger declaration file content or url

Replace

.\swagger-codegen\modules\swagger-codegen\src\test\resources\2_0\petstore-flask.yaml

with

petstore-flask.zip

Command line used for generation

bin\windows\python3-flask-petstore.bat

Steps to reproduce

Use this API
http://localhost:8080/v2/ui/#!/pet/add_pet
http://localhost:8080/v2/ui/#!/pet/update_pet

Related issues/PRs

Not found

Suggest a fix/enhancement

To be defined

Start with modules/swagger-codegen/src/main/resources/python-flask/controller.mustache and the supplied 2_0/petstore-flask.yaml definition. Reproduce the issue with bin\windows\python3-flask-petstore.bat and inspect the generated add_pet handler for the required header parameter. Done means the generated stub is called correctly for the documented header and body parameters, with a regression test or fixture capturing the behavior.