feat(hyperswitch): add CreateRefund to client

veza-backend-api/internal/services/hyperswitch/client.go

@@ -137,3 +137,53 @@ func (c *Client) GetPayment(ctx context.Context, paymentID string) (*PaymentStat
 	}
 	return &out, nil
 }
+
+// CreateRefundRequest is the request body for POST /refunds (v0.403 R2)
+type CreateRefundRequest struct {
+	PaymentID  string `json:"payment_id"`
+	Amount     *int64 `json:"amount,omitempty"` // nil = full refund
+	Reason     string `json:"reason,omitempty"`
+	RefundType string `json:"refund_type,omitempty"` // "instant" or "scheduled"
+}
+
+// RefundResponse is the response from POST /refunds
+type RefundResponse struct {
+	RefundID  string `json:"refund_id"`
+	PaymentID string `json:"payment_id"`
+	Amount    int64  `json:"amount"`
+	Currency  string `json:"currency"`
+	Status    string `json:"status"`
+}
+
+// CreateRefund creates a refund against a payment (v0.403 R2)
+func (c *Client) CreateRefund(ctx context.Context, paymentID string, amount *int64, reason string) (*RefundResponse, error) {
+	reqBody := CreateRefundRequest{
+		PaymentID:  paymentID,
+		Amount:     amount,
+		Reason:     reason,
+		RefundType: "instant",
+	}
+	body, err := json.Marshal(reqBody)
+	if err != nil {
+		return nil, fmt.Errorf("marshal refund request: %w", err)
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/refunds", bytes.NewReader(body))
+	if err != nil {
+		return nil, fmt.Errorf("create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("api-key", c.apiKey)
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("http request: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("hyperswitch create refund failed: status %d", resp.StatusCode)
+	}
+	var out RefundResponse
+	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
+		return nil, fmt.Errorf("decode response: %w", err)
+	}
+	return &out, nil
+}

veza-backend-api/internal/services/hyperswitch/provider.go

@@ -28,3 +28,9 @@ func (p *Provider) CreatePayment(ctx context.Context, amount int64, currency, or
 func (p *Provider) GetPayment(ctx context.Context, paymentID string) (string, error) {
 	return p.client.GetPaymentStatus(ctx, paymentID)
 }
+
+// Refund creates a refund in Hyperswitch (v0.403 R2).
+func (p *Provider) Refund(ctx context.Context, paymentID string, amount *int64, reason string) error {
+	_, err := p.client.CreateRefund(ctx, paymentID, amount, reason)
+	return err
+}