[REQ] Respect `default` parameters in aspnetcore generator

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Default parameters are not added to the generated controller methods by the aspnetcore generator

actual signature output:

public virtual IActionResult AGet([FromQuery (Name = "b")]bool? b)

expected:

public virtual IActionResult AGet([FromQuery (Name = "b")]bool b = false)

openapi-generator version

docker image b28b21d6f3da

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: example
  version: 0.0.1
paths:
  /a:
    get:
      parameters:
        - name: b
          in: query
          schema:
            type: boolean
            default: false
      responses:
        '200':
          description: OK

Generation Details

Docker & git-bash for Windows

Steps to reproduce

1. add the above to the file example.yml in an otherwise empty folder
2. run the following bash command from that folder:

rm -rf out && MSYS_NO_PATHCONV=1 docker run --rm -v "${PWD}:/local" \
  openapitools/openapi-generator-cli generate \
  --input-spec "/local/example.yml" \
  --output "/local/out/aspnetcore" \
  --generator-name aspnetcore

Start with the example.yml reproduction and run the documented Docker command using the aspnetcore generator. Inspect the generated controller method signature; done means the query parameter's declared default is preserved as a non-nullable bool with = false rather than becoming nullable.