PreApproval
data class PreApproval(val payer: Party, val payerCurrency: String, val payerMessage: String? = null, val validityTime: Int)
Represents a Collection pre-approval request sent to the MTN MOMO Pre-approval API.
A pre-approval authorises the merchant to debit the payer's account up to an implied amount without requiring explicit per-transaction approval. The authorisation expires after validityTime seconds. Subsequent charges against the pre-approval use the standard Request-to-Pay flow.