Rails validation error messages: Add response code to default validators

Question

I am looking for a best-practise / solution to render responses with different http-response codes than 422 - unprocessable entity.

I have a simple validator:

validates :name, presence: true, uniqueness: {message: 'duplicate names are not allowed!'}

I want to return status code 409 - Conflict (:conflict) when this validation fails. Possible solution:

Add status code to errors hash, e.g. errors.add(status_code: '409'). Then either render the status code from errors, or render 422 if multiple exists.

The problem with the above solution is that I do not know how to call the errors.add function on a 'standard' validator.

My render code:

if model.save
    render json: model, status: :created
  else
    render json: model.errors, status: :unprocessable_entity
  end

Which I would like to extent that it can render different status codes based on validation results.