Remove IsRefundableStatus() function. Probably it shouldn't be a part…

… of this library

README.md

@@ -140,13 +140,6 @@ fmt.Println("resend scheduled for %d notifications", res.Count)
   httpResp, err := client.PostRequest(&myCouponUpgradeRequest{PaymentID: "3293", Coupon: "whatever"})
   ```
 
-- `tinkoff.IsRefundableStatus(s)` allows you to check if the payment can be refunded according to policies provided by Tinkoff API doc:
-  ```go
-  if !tinkoff.IsRefundableStatus(payment.Status) {
-      return errors.New("payment can't be refunded")
-  }
-  ```
-
 ## References
 The code in this repo based on some code from [koorgoo/tinkoff](https://github.com/koorgoo/tinkoff). Differences:
 - Support for API v2

status.go

@@ -20,13 +20,3 @@ const (
 	StatusPartialRefunded = "PARTIAL_REFUNDED" // Возвращен частично
 	StatusRefunded        = "REFUNDED"         // Возвращен полностью
 )
-
-func IsRefundableStatus(status string) bool {
-	switch status {
-	case StatusNew,
-		StatusAuthorized,
-		StatusConfirmed:
-		return true
-	}
-	return false
-}