horse: use straight front type in racecourse api

race.go

@@ -46,11 +46,9 @@ type RacecourseSpan struct {
 	Start float32 `json:"start"`
 	// End is the distance in meters along the track at which the span ends.
 	End float32 `json:"end"`
-	// Straight is whether the span is formally a straight.
-	Straight bool `json:"straight,omitzero"`
-	// FarStraight is whether the span is the backstretch.
-	// If true, then Straight is also true.
-	FarStraight bool `json:"far_straight,omitzero"`
+	// Straight is the straight type if the span is formally a straight.
+	// 1 indicates the front stretch and 2 the backstretch.
+	Straight int8 `json:"straight,omitzero"`
 	// Corner is the corner number of the span, or zero if not a corner.
 	Corner int8 `json:"corner,omitzero"`
 }