text: Title: Support for Free-Form Query Parameters
  Body: **Is your feature request related to a problem? Please describe.**
  
  Given an API that accepts arbitrarily-named query parameters like:
  
  /my-endpoint/?dynamic_param1=value&dynamic_param2=value2
  
  We'd like to be able to append arbitrary key/values to the query string search.
  
  Given a current YAML snippet like:
  
  ```yaml
      parameters:
          - in: query
            name: dynamicFields
            schema:
              type: object
              additionalProperties: true
  ```
  
  The parameter generated is `schema_field: Union[Unset, ModelNameSchemaField] = UNSET`, and it's also sent as the parameter named `schema_field` instead of using the arbitrary keys.
  
  **Describe the solution you'd like**
  
  Generate the parameter above with `additionalProperties` as `schema_field: Union[Unset, None, Dict[str, Any]] = UNSET`. When `schema_field` is a `dict`, it will then send values for all keys in the query parameters instead of as `schema_field`.
  
  If multiple parameters are defined having `additionalProperties`, it will treat all of them as arbitrary keys. If two parameters were to define the same dynamically named key, we make no guarantees about which one is sent. I imagine it would be the last parameter encountered with `additionalProperties`. Alternatively, we could raise an exception instead of making silent assumptions about the collision.
  
  **Describe alternatives you've considered**
  
  Rather than modeling the field in Open API, allow every GET method to accept an `additional_properties: Dict[str, str]` parameter which would append all the keys as query parameters. The name `additional_properties` might need to be configurable to avoid collision with APIs using that parameter name already.
  