feat: create XRayInstrument

[pokryfka]

No description provided.

[slashmo]

Thanks again for creating this PR, looks great already 👍
I've added some comments inline.

[pokryfka]

@slashmo thank you for the comments and snippets, I will copy that and commit. feel welcome to push changes, just until it works more or less and tests pass (those I created fail miserably lol) let's consider feature/instrument the integration branch for the instrument related changes.

The refactoring changes I noted in my head yesterday:

• expose subsegment name (currently internal)
• define Context type, this will be equivalent of the TracingHeader but it feels weird to use "TracingHeader" in Segment
• add attribute of Context type to subsegment (will contain traceId, optionally parent and samplng decision which are separate attributes at the moment; the sampling decision is related with isRecording defined in Span)
• the Context type should eventually be the BaggageContext though it may be in 2nd iteration of changes
• extend annotations and metadata interface to let remove existing values to match SpanAttributes

[pokryfka]

well, the tests defined yesterday pass now - so its a small progress ;-)
there are more tests which, once defined, will fail though

[codecov-commenter]

Codecov Report

Merging #16 into master will increase coverage by 0.64%.
The diff coverage is 91.37%.

@@            Coverage Diff             @@
##           master      #16      +/-   ##
==========================================
+ Coverage   77.11%   77.76%   +0.64%     
==========================================
  Files          29       31       +2     
  Lines        1219     1277      +58     
==========================================
+ Hits          940      993      +53     
- Misses        279      284       +5     

Impacted Files	Coverage Δ
Sources/AWSXRayInstrument/Span.swift	89.36% <89.36%> (ø)
Sources/AWSXRayInstrument/Instrument.swift	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c505ac2...e09bc8e. Read the comment docs.

[pokryfka]

@ktoso @slashmo first version with Baggage, please let me know if it makes sense, will highlight specific questions/issues in the code

out now, will recheck it in the evening as well as pull in any related changes from gsoc-swift-tracing

[pokryfka]

@slashmo @ktoso

I deployed a "hello world" lambda a few weeks ago when testing XRayRecorder;
it creates a few subsegments:

• the endpoint: https://d41u83stcl.execute-api.us-east-1.amazonaws.com/Prod/hello/
• code for reference: https://github.com/pokryfka/swift-aws-lambda-template/blob/master/Sources/HelloWorldAPI/main.swift

result from AWSXRayInstrumentExample (which called the url above using BetterHTTPClient):

note that currently events are recorded as both subsegments and metadata:

[slashmo]

there is "hello world" lambda I deployed which creates a few subsegments:

Wow, that's awesome! 🎉

[ktoso]

Ah thanks a lot, that explains how metadata is presented. I guess yeah events in there sound like an okey way to at least show them to users somehow 👍