StringConversionSink class

This class provides an interface for converters to efficiently transmit String data.

Instead of limiting the interface to one non-chunked String it accepts partial strings or can be transformed into a byte sink that accepts UTF-8 code units.

This abstract class will likely get more methods over time. Implementers are urged to extend StringConversionSinkBase or to mix in StringConversionSinkMixin, to ensure that their class covers the newly added methods.