[SDK + Otlp] Support loading envvars from IConfiguration

[CodeBlanch]

Relates to #2980
Relates to #3720
Relates to #3639

Changes

• Rename SdkConfiguration -> SdkLimitOptions & remove static coupling.
• Support loading envvars for OtlpExporterOptions, SdkLimitOptions, & MetricReaderOptions from IConfiguration

TODOs

• Appropriate CHANGELOG.md updated for non-trivial changes
• Unit tests
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #3760 (41c55d1) into main (0feebf3) will increase coverage by 0.17%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3760      +/-   ##
==========================================
+ Coverage   87.04%   87.21%   +0.17%     
==========================================
  Files         278      277       -1     
  Lines       10167    10209      +42     
==========================================
+ Hits         8850     8904      +54     
+ Misses       1317     1305      -12     

Impacted Files	Coverage Δ
...metryProtocol/Implementation/ActivityExtensions.cs	91.89% <100.00%> (+0.13%)	⬆️
...etryProtocol/Implementation/LogRecordExtensions.cs	85.88% <100.00%> (ø)
...elemetryProtocol/Implementation/SdkLimitOptions.cs	100.00% <100.00%> (ø)
...orter.OpenTelemetryProtocol/OtlpExporterOptions.cs	100.00% <100.00%> (ø)
....Exporter.OpenTelemetryProtocol/OtlpLogExporter.cs	75.00% <100.00%> (+5.00%)	⬆️
...nTelemetryProtocol/OtlpMetricExporterExtensions.cs	95.55% <100.00%> (+1.43%)	⬆️
...xporter.OpenTelemetryProtocol/OtlpTraceExporter.cs	65.38% <100.00%> (+29.02%)	⬆️
...metryProtocol/OtlpTraceExporterHelperExtensions.cs	94.73% <100.00%> (+2.73%)	⬆️
...lder/ProviderBuilderServiceCollectionExtensions.cs	100.00% <100.00%> (ø)
...ry/Internal/PeriodicExportingMetricReaderHelper.cs	100.00% <100.00%> (ø)
... and 10 more

[cijothomas]

How would users use this feature? Its a bit misleading, as the SDK itself does not enforce any of the limits from this class...

[CodeBlanch]

I reverted the SdkOptions changes on this PR. But I don't necessarily have an issue with the above. SDK is doing many things without enforcement! For example, up to each exporter author to correctly support every feature of SDK (Resource, Scopes, Histograms, etc.) 🤣 You know how the spec has the compliance matrix? Maybe we should have one too just for the different .NET bits floating around? Maintenance headache but there really should be some way for users to check what parts of the spec/SDK the thing they are consuming supports.

[alanwest]

Just to clarify my understanding of things...

Let's say I set OTEL_EXPORTER_OTLP_ENDPOINT=http://my-collector.com and I also have some json config like:

{
  "MyOtlpExporterOptions": {
     "Headers": "api-key=abc123" 
  }
}

Then I do this somewhere.

builder.Services.Configure<OtlpExporterOptions>(builder.Configuration.GetSection("MyOtlpExporterOptions"));

Will I get the headers setting from the json and the endpoint setting from the environment variable?

[CodeBlanch]

Will I get the headers setting from the json and the endpoint setting from the environment variable?

Yes!

[alanwest]

Just testing my understanding of things with a somewhat contrived question... but this LGTM!