ServerSentEventReader
An SSE event reader that reads lines from an SSE stream and composes them
            into SSE events.
            See SSE specification: https://html.spec.whatwg.org/multipage/server-sent-events.html
            
                
Synchronously retrieves the next server-sent event from the underlying stream, blocking until a new event is
            available and returning null once no further data is present on the stream.
            
Asynchronously retrieves the next server-sent event from the underlying stream, blocking until a new event is
            available and returning null once no further data is present on the stream.