function overrideFormData(receiver, donor) {
    for (const key of donor.keys()) {
      receiver.delete(key)
    }
    donor.forEach(function(value, key) {
      receiver.append(key, value)
    })
    return receiver
  }
Override values in the one FormData with those from another.
@param {FormData} receiver the formdata that will be mutated
@param {FormData} donor the formdata that will provide the overriding values
@returns {FormData} the {@linkcode receiver}