GetRecorder returns an appropriate recorder based on the value of MetricsRecorder.

NewRelicFromContext creates a new NewRelic recorder from the given context, or a NoOp recorder if there is no NewRelic transaction in the context.

MetricsRecorder is used by the GetRecorder function to determine which recorder to return.

NewRelic implements the transaction.metrics interface.

NoOp satisfies the Recorder interface, but does nothing.

Recorder is an interface for recording metrics about the application.