• What is the current behavior?

DjangoModelFormMutation has the option to change the input name of the mutation, but it is always set to "input" regardless of value. Like so:

class SendMessageMutation(DjangoModelFormMutation):
    message = relay.Node.Field(MessageType)

    class Meta:
        form_class = SendMessageForm
        input_field_name = "message"

• What is the expected behavior?
  Documentation states you can set input_field_name in the meta:
  https://docs.graphene-python.org/projects/django/en/latest/mutations/

• Please tell us about your environment:

  • Version: graphene-django: 2.13.0, graphene 2.1.8
  • Platform: Django 3.0.11