[Extensions] Update BaggageActivityProcessor to use baggage key predicate

[MikeGoldsmith]

Fixes #1695

Changes

• Updates the BaggageActivityProcessor to require a predicate as a constructor parameter
• Use the predicate function to determine which baggage entries are added to the new activity
• Add a public static predicate that allows all baggage entries
• Update README with examples of using the all baggage and a custom predicates

For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.71%. Comparing base (71655ce) to head (ecf3160).
Report is 359 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1816       +/-   ##
===========================================
+ Coverage   73.91%   85.71%   +11.79%     
===========================================
  Files         267        8      -259     
  Lines        9615      140     -9475     
===========================================
- Hits         7107      120     -6987     
+ Misses       2508       20     -2488     

Flag	Coverage Δ
unittests-Extensions	85.71% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...ons/Internal/OpenTelemetryExtensionsEventSource.cs	53.84% <100.00%> (+8.39%)	⬆️
...metry.Extensions/Trace/BaggageActivityProcessor.cs	100.00% <100.00%> (ø)
...etry.Extensions/TracerProviderBuilderExtensions.cs	94.44% <100.00%> (+27.77%)	⬆️

... and 265 files with indirect coverage changes

[MikeGoldsmith]

Ping @open-telemetry/dotnet-contrib-approvers @open-telemetry/dotnet-contrib-maintainers - please can you take a look?

[MikeGoldsmith]

Thanks for the feedback @CodeBlanch - I've made some updates, please take another look.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[cijothomas]

I am generally not in favor of allowing arbitrary user code executions (see #1816 (comment)), but given there is an existing precedent in this component, not a blocker.

[Kielek]

@MikeGoldsmith, could you please merge main branch to PR branch (or allow us to do this)?

@CodeBlanch, do you have any other comments?

[MikeGoldsmith]

@Kielek updated again, let me know if you need anything else.

[cijothomas]

@Kielek updated again, let me know if you need anything else.

Can you fix the CI failures? Looks like some minor import statements causing CI to fail.

[MikeGoldsmith]

Yeah, sure. I wasn't sure if they were intermittent / unrelated failures as they only occurred in the merge from main commits. I'll fix up the PR tomorrow.

[Kielek]

@MikeGoldsmith, it is the reason #1927 (or one of the previous PR for the same topic), unfortunately needs to be manually adjusted for all existing PRs.

EDIT: Isee that you are contirbuting from corporate fork. If you could do from your personal, you can enable Allow maintainers to modify PR/brach. Then we can push trivial fixes/merges there without asking you.

[MikeGoldsmith]

@Kielek @cijothomas removed the unused using statements and CI is passing now - thanks for your help 😄