Reapply "feat(loyalty): EnakPoint & EnakCoin" (#32)

This reverts commit 4e24f9bbb0.

internal/contract/wallet_contract.go

@@ -0,0 +1,31 @@
+package contract
+
+// AdjustCustomerWalletRequest is POST /marketing/customers/:id/wallet/adjust
+// (docs/prd-point-coin.md F7).
+type AdjustCustomerWalletRequest struct {
+	// POINT or COIN.
+	Currency string `json:"currency"`
+	// Signed: positive adds to the balance, negative takes from it. Never zero.
+	Amount int64  `json:"amount"`
+	Reason string `json:"reason"`
+	// Optional. Sending the same key again returns the first result instead of
+	// adjusting twice, so a retried request is safe.
+	IdempotencyKey string `json:"idempotency_key"`
+}
+
+// ExchangeCoinsRequest is POST /customer/wallet/exchange (docs/prd-point-coin.md F4).
+// The Idempotency-Key header is required.
+type ExchangeCoinsRequest struct {
+	Coins int64  `json:"coins" binding:"required,min=1"`
+	Pin   string `json:"pin" binding:"required"`
+}
+
+// TransferWalletRequest is POST /customer/wallet/transfer (docs/prd-point-coin.md F5).
+// The Idempotency-Key header is required.
+type TransferWalletRequest struct {
+	// POINT or COIN.
+	Currency       string `json:"currency" binding:"required"`
+	Amount         int64  `json:"amount" binding:"required,min=1"`
+	RecipientPhone string `json:"recipient_phone" binding:"required"`
+	Pin            string `json:"pin" binding:"required"`
+}