/// - derives the [`InvoiceRequest::payer_id`] such that a different key can be used for each
/// request, and
/// - sets the [`InvoiceRequest::metadata`] when [`InvoiceRequestBuilder::build`] is called such
/// - derives the [`InvoiceRequest::payer_id`] such that a different key can be used for each
/// request, and
/// - sets the [`InvoiceRequest::metadata`] when [`InvoiceRequestBuilder::build`] is called such