funding+lnwallet: ensure max_htlc_value_in_flight smaller than capacity

Return an error to the remote if larger.

lnwallet/errors.go

@@ -132,6 +132,16 @@ func ErrNumConfsTooLarge(numConfs, maxNumConfs uint32) error {
 	}
 }
 
+// ErrMaxValueInFlightTooLarge returns an error indicating that the 'max HTLC
+// value in flight' the remote required is too large to be accepted.
+func ErrMaxValueInFlightTooLarge(maxValInFlight,
+	maxMaxValInFlight lnwire.MilliSatoshi) ReservationError {
+	return ReservationError{
+		fmt.Errorf("maxValueInFlight too large: %v, max is %v",
+			maxValInFlight, maxMaxValInFlight),
+	}
+}
+
 // ErrChanTooSmall returns an error indicating that an incoming channel request
 // was too small. We'll reject any incoming channels if they're below our
 // configured value for the min channel size we'll accept.