add OpenRTB 2.6 'rwdd' field for impression

impression.go

@@ -32,9 +32,10 @@ type Impression struct {
 	BidFloor              float64         `json:"bidfloor,omitempty"`          // Bid floor for this impression in CPM
 	BidFloorCurrency      string          `json:"bidfloorcur,omitempty"`       // Currency of bid floor
 	Secure                NumberOrString  `json:"secure,omitempty"`            // Flag to indicate whether the impression requires secure HTTPS URL creative assets and markup.
-	Quantity              *Quantity       `json:"qty,omitempty"`          // Includes the impression multiplier, and describes its source.
-	Exp                   int             `json:"exp,omitempty"`          // Advisory as to the number of seconds that may elapse between the auction and the actual impression.
-	IFrameBusters         []string        `json:"iframebuster,omitempty"` // Array of names for supportediframe busters.
+	Quantity              *Quantity       `json:"qty,omitempty"`               // Includes the impression multiplier, and describes its source.
+	Exp                   int             `json:"exp,omitempty"`               // Advisory as to the number of seconds that may elapse between the auction and the actual impression.
+	IFrameBusters         []string        `json:"iframebuster,omitempty"`      // Array of names for supportediframe busters.
+	Rewarded              int             `json:"rwdd,omitempty"`              // Impression is rewarded, Default: 0 ("1": yes, "0": no)
 	Ext                   json.RawMessage `json:"ext,omitempty"`
 }