feat: add payment module

modules/payment/schemas/transaction-participant.ts

@@ -0,0 +1,17 @@
+import z from "zod";
+
+/*
+ |--------------------------------------------------------------------------------
+ | Transaction Participant
+ |--------------------------------------------------------------------------------
+ |
+ | A participant is either an internal account or an external entity.
+ |
+ */
+
+export const TransactionParticipantType = z.union([
+  z.literal("account").describe("Participant is an internal account on the ledger"),
+  z.literal("external").describe("Participant is a opaque external entity"),
+]);
+
+export type TransactionParticipant = z.output<typeof TransactionParticipantType>;