Double check isRecording implementation

[ktoso]

Is recording should be:

IsRecording

Returns true if this Span is recording information like events with the AddEvent operation, attributes using SetAttributes, status with SetStatus, etc.

After a Span is ended, it usually becomes non-recording and thus IsRecording SHOULD consequently return false for ended Spans. Note: Streaming implementations, where it is not known if a span is ended, are one expected case where IsRecording cannot change after ending a Span.

IsRecording SHOULD NOT take any parameters.

This flag SHOULD be used to avoid expensive computations of a Span attributes or events in case when a Span is definitely not recorded. Note that any child span's recording is determined independently from the value of this flag (typically based on the sampled flag of a TraceFlags on SpanContext).

This flag may be true despite the entire trace being sampled out. This allows to record and process information about the individual Span without sending it to the backend. An example of this scenario may be recording and processing of all incoming requests for the processing and building of SLA/SLO latency charts while sending only a subset - sampled spans - to the backend. See also the sampling section of SDK design.

Users of the API should only access the IsRecording property when instrumenting code and never access SampledFlag unless used in context propagators.

but it seems we just store it as true and never change it 🤔

Should we change it to false once endSpan is done?