GeoCircle constructor
Creates a new GeoCircle with the given center and radius.
Throws AssertionError if radius is not positive.
Example:
final circle = GeoCircle(
center: GeoPoint(latitude: 37.7749, longitude: -122.4194),
radius: 1000, // 1 kilometer
);
Implementation
const GeoCircle({
required this.center,
required this.radius,
}) : assert(radius > 0, 'Radius must be greater than zero');