[Feature Request] Add OpenTelemetry Support

[slang25]

It would be great if out of the box JustSaying used ActivitySource that ships with .NET 5 (and the System.Diagnostics.DiagnosticsSource package for other TFMs).

See here:
https://devblogs.microsoft.com/dotnet/opentelemetry-net-reaches-v1-0/#library-authors

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[slang25]

I've been giving this some thought and think that we should make progress on this issue soon.
I'm thinking having an extra default middleware that does the ActivitySource goodness is the way to go, we already have an extensibility point for metrics, so could optionally add an out-of-the-box implementation of that too.

It would be cool to add use of AWSXRayPropagator (see here) but I'm hesitant to add a dependency to the main JustSaying package. Could we do this with extensible enrichment and a separate package? Would like peoples thoughts.