IndicatorType is a special type that can be used to signal to consumers of Fudge encoded data that there is a field present, but that the contents aren't meaningful in any way. It is the only 0-sized fixed width type in the Fudge type system.
It is commonly used for the following purposes:
- As a 0-byte boolean (if the field is there, true; else false)
- To clear a message when sending delta updates (previously field foo had the value 42; now, clear it from your current state)
In the reference implementations, there is a singleton instance of IndicatorType that is returned for all field references.