Refund from capture endpoint function (#141)

* Capture refund API call

* .

order.go

@@ -94,3 +94,19 @@ func (c *Client) CaptureOrder(orderID string, captureOrderRequest CaptureOrderRe
 
 	return capture, nil
 }
+
+// RefundCapture - https://developer.paypal.com/docs/api/payments/v2/#captures_refund
+// Endpoint: POST /v2/payments/captures/ID/refund
+func (c *Client) RefundCapture(captureID string, refundCaptureRequest RefundCaptureRequest) (*RefundResponse, error) {
+	refund := &RefundResponse{}
+
+	req, err := c.NewRequest("POST", fmt.Sprintf("%s%s", c.APIBase, "/v2/payments/captures/"+captureID+"/refund"), refundCaptureRequest)
+	if err != nil {
+		return refund, err
+	}
+
+	if err = c.SendWithAuth(req, refund); err != nil {
+		return refund, err
+	}
+	return refund, nil
+}

types.go

@@ -243,6 +243,13 @@ type (
 		PaymentSource *PaymentSource `json:"payment_source"`
 	}
 
+	// RefundOrderRequest - https://developer.paypal.com/docs/api/payments/v2/#captures_refund
+	RefundCaptureRequest struct {
+		Amount      *Money `json:"amount,omitempty"`
+		InvoiceID   string `json:"invoice_id,omitempty"`
+		NoteToPayer string `json:"note_to_payer,omitempty"`
+	}
+
 	// BatchHeader struct
 	BatchHeader struct {
 		Amount            *AmountPayout      `json:"amount,omitempty"`