WIP: Datadog Baggage API

[rachelyangdog]

What does this PR do?

Adding baggage API. This is the first PR to add baggage functionality to dd-trace-go and only adds the public API methods.

Motivation

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.
• For internal contributors, a matching PR should be created to the v2-dev branch and reviewed by @DataDog/apm-go.

Unsure? Have a question? Request a review!

[datadog-datadog-prod-us1]

Datadog Report

Branch report: rachel.yang/baggage-api-context
Commit report: f9c9602
Test service: dd-trace-go

❌ 1 Failed (0 Known Flaky), 5129 Passed, 70 Skipped, 2m 38.36s Total Time

❌ Failed Tests (1)

• TestWrapConsumerGroupHandler - gopkg.in/DataDog/dd-trace-go.v1/contrib/IBM/sarama.v1 - Details

  Expand for error

   Failed
   
   === RUN   TestWrapConsumerGroupHandler
   2025/01/10 19:04:33 Sarama consumer up and running!...
       consumer_group_test.go:88: 
           	Error Trace:	/home/runner/work/dd-trace-go/dd-trace-go/contrib/IBM/sarama.v1/consumer_group_test.go:88
           	Error:      	"[
           	            	name: kafka.produce
           	            	tags: map[string]interface {}{"component":"IBM/sarama", "messaging.kafka.partition":0, "messaging.system":"kafka", "offset":0, "resource.name":"Produce Topic gotest_ibm_sarama", "service.name":"kafka", "span.kind":"producer", "span.type":"queue"}
           	            	start: 2025-01-10 19:04:33.05564188 +0000 UTC m=+0.927038579
   ...
  

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-10 19:42:22

Comparing candidate commit a481ced in PR branch rachel.yang/baggage-api-context with baseline commit 5a8a82c in branch main.

Found 0 performance improvements and 3 performance regressions! Performance is the same for 56 metrics, 0 unstable metrics.

scenario:BenchmarkSetTagString-24

• 🟥 execution_time [+6.902ns; +13.258ns] or [+6.005%; +11.535%]

scenario:BenchmarkSetTagStringPtr-24

• 🟥 execution_time [+4.056ns; +5.304ns] or [+2.349%; +3.072%]

scenario:BenchmarkSetTagStringer-24

• 🟥 execution_time [+6.712ns; +14.048ns] or [+4.672%; +9.778%]

[mtoffl01]

Did a light review with some comments - go ahead and address those and then I can take a second pass!