toICalString method
Implementation
String toICalString() {
final buffer = StringBuffer();
buffer.writeln('BEGIN:VFREEBUSY');
buffer.writeln('DTSTART:${start.toUtc().toIso8601String()}Z');
buffer.writeln('DTEND:${end.toUtc().toIso8601String()}Z');
buffer.writeln(
'FREEBUSY:${busy.map((range) => range.toICalString()).join('/')}');
buffer.writeln('END:VFREEBUSY');
return buffer.toString();
}