SseStream

Attempt to load an entire event. For each entire event we load, send them to be handled.

Given an event string, get all the fields in the event. It is assumed there is one field per line, but that field names can be duplicated, indicating to append the new value to the previous value

Add more text to the buffer

Indicate that there is no more text to be added to the buffer (ie - our source material is done)

Get the next chunk that is coming from the stream. This chunk may be null, usually indicating the last chunk in the stream.