Payment Rails per Country

// the shared model the core and the app speak
type Destination =
  | { kind: 'bank_account'; country: 'NG' | 'GH'; bankCode: string; accountNumber: string }
  | { kind: 'mobile_wallet'; country: 'KE'; msisdn: string }
  | { kind: 'alias'; country: 'BR' | 'IN'; alias: string }
  | { kind: 'iban'; country: string; iban: string };

type TransferState = 'draft' | 'submitted' | 'pending' | 'completed' | 'failed' | 'reversed' | 'unknown';

interface RailAdapter {
  validate(d: Destination): Result<void, FieldError[]>;
  resolveRecipient(d: Destination): Promise<{ name: string } | { notFound: true }>;   // name enquiry, alias lookup
  submit(t: Transfer, idempotencyKey: string): Promise<TransferState>;
  status(ref: string): Promise<TransferState>;                                         // for unknown and pending
  mapCode(code: string): { state: TransferState; messageKey: string };
}