Implement Serialize & Deserialize for Sampler

[cecton]

Hello 👋

I noticed that a few types like Resource and KeyValue implement Serialize and
Deserialize which is very handy for me because I can integrate the different
parameter into a configuration struct.

Unfortunately it is not yet implemented for Sampler so I had to implement it
on my crate but I think this could be beneficial for others.

Let me know what you think

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Cecile Tonglet (893b7a4)

[codecov]

Codecov Report

Merging #622 (a1d12e4) into main (a0899d9) will decrease coverage by 0.11%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #622      +/-   ##
==========================================
- Coverage   62.08%   61.97%   -0.12%     
==========================================
  Files          95       95              
  Lines        7681     7681              
==========================================
- Hits         4769     4760       -9     
- Misses       2912     2921       +9     

Impacted Files	Coverage Δ
opentelemetry/src/sdk/trace/sampler.rs	92.98% <0.00%> (+0.06%)	⬆️
opentelemetry-datadog/src/exporter/model/v03.rs	91.66% <0.00%> (-4.17%)	⬇️
opentelemetry-datadog/src/exporter/model/v05.rs	92.15% <0.00%> (-3.93%)	⬇️
opentelemetry-jaeger/src/exporter/collector.rs	67.85% <0.00%> (-3.58%)	⬇️
opentelemetry/src/global/error_handler.rs	42.10% <0.00%> (-2.34%)	⬇️
opentelemetry-jaeger/src/exporter/uploader.rs	24.00% <0.00%> (-2.09%)	⬇️
opentelemetry/src/metrics/registry.rs	49.41% <0.00%> (-1.20%)	⬇️
opentelemetry/src/sdk/trace/evicted_hash_map.rs	65.16% <0.00%> (-1.13%)	⬇️
opentelemetry-datadog/src/lib.rs	91.45% <0.00%> (-0.92%)	⬇️
opentelemetry/src/context.rs	92.06% <0.00%> (-0.80%)	⬇️
... and 24 more

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[TommyCpp]

👍 Overall looks good. Nice job! The only thing we might want to examine is the current serialization/de-serialization process eliminated the ParentBased variant. I don't think it would cause any issue but I think the serialization process shouldn't change the variant.

[cecton]

omg what am I doing. Why do I even bother implementing them manually 🤯

Oh I know... I had in my own crate because I don't own the type. Then I copied here thinking I had too.

@TommyCpp this should be much easier to review. I'm not sure the test is useful at all. I suggest we delete it entirely.

[TommyCpp]

Looks good. Thanks

[cecton]

Hey @TommyCpp I tried to lock the version on my side but it's actually very complicated. Because it's linked to tracing I have to fork tracing too and replace all the tracin dependencies in my project. Would it be possible for you to make a release?

[cecton]

@TommyCpp never mind, I just tried with the patch syntax instead of pinning the version in the dependency and it worked like a charm. The release can wait :)