Implementing ExtendedTextMapGetter in grpc-1.6 instrumentation

[xiepuhuan]

Related to #12868

[xiepuhuan]

Do I need to add unit testing to GrpcRequestGetter?

[trask]

cc @jamesmoessis

[jamesmoessis]

Nice work @xiepuhuan

I'm not overly familiar with the gRPC library, but this looks good to me. A unit test would give further confidence that multi-extraction is working. However if it has @trask's approval without the extra test I assume it's ok :)

[trask]

A unit test would give further confidence that multi-extraction is working.

I opened #13016 to track this, @xiepuhuan wdyt?

[xiepuhuan]

A unit test would give further confidence that multi-extraction is working.

I opened #13016 to track this, @xiepuhuan wdyt?

I will complete it immediately.

[vivvdvooren]

@xiepuhuan I have been trying to use the latest version of opentelemetry-grpc-1.6 (2.14-alpha) and I get an error due to missing class io/opentelemetry/context/propagation/internal/ExtendedTextMapGetter
Which library should supply this class?

[xiepuhuan]

@xiepuhuan I have been trying to use the latest version of opentelemetry-grpc-1.6 (2.14-alpha) and I get an error due to missing class io/opentelemetry/context/propagation/internal/ExtendedTextMapGetter Which library should supply this class?

io.opentelemetry:opentelemetry-context:1.48.0