Update OTEL_EXPORTER_JAEGER_PROTOCOL parsing

[Kielek]

Fixes #2910.

Changes

Align the OTEL_EXPORTER_JAEGER_PROTOCOL parsing with the spec

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

• Appropriate CHANGELOG.md updated for non-trivial changes

[pellared]

I think this table is more about .NET API.

I would consider adding a footnote to the OTEL_EXPORTER_JAEGER_PROTOCOL or find another way to describe it in Environment Variables section. As for me it can be done like in https://github.com/open-telemetry/opentelemetry-dotnet/tree/main/src/OpenTelemetry.Exporter.OpenTelemetryProtocol#environment-variables to remain consistent.

[Kielek]

fixed c1b1401

[codecov]

Codecov Report

Merging #2914 (f210af0) into main (f234829) will increase coverage by 0.55%.
The diff coverage is 100.00%.

❗ Current head f210af0 differs from pull request most recent head 4a53de2. Consider uploading reports for the commit 4a53de2 to get more accurate results

@@            Coverage Diff             @@
##             main    #2914      +/-   ##
==========================================
+ Coverage   83.88%   84.43%   +0.55%     
==========================================
  Files         253      253              
  Lines        8910     8901       -9     
==========================================
+ Hits         7474     7516      +42     
+ Misses       1436     1385      -51     

Impacted Files	Coverage Δ
...Telemetry.Exporter.Jaeger/JaegerExporterOptions.cs	100.00% <100.00%> (+9.52%)	⬆️
...Exporter.Jaeger/JaegerExporterOptionsExtensions.cs	100.00% <100.00%> (ø)
...orter.OpenTelemetryProtocol/OtlpExporterOptions.cs	100.00% <100.00%> (ø)
...penTelemetry/Internal/EnvironmentVariableHelper.cs	80.00% <100.00%> (ø)
...ZPages/Implementation/ZPagesExporterEventSource.cs	56.25% <0.00%> (-6.25%)	⬇️
src/OpenTelemetry/Metrics/MetricReaderOptions.cs
...OpenTelemetry/Metrics/BaseExportingMetricReader.cs	85.00% <0.00%> (+1.66%)	⬆️
...nTelemetryProtocol/OtlpMetricExporterExtensions.cs	100.00% <0.00%> (+35.71%)	⬆️
... and 1 more

[pellared]

subjective opinion (no need to be addressed)

As rule of thumb, I avoid adding extension methods for BCL classes unless these are very generic. This method is only used in JaegerExporterOptions and tests so I would rather not add is as an extension method to string. Personally, I would move it to JaegerExporterOptions class with following signature:

internal static JaegerExportProtocol? ParseProtocol(string value)

or

internal static bool ParseProtocol(string value, out JaegerExportProtocol result)

[Kielek]

In general, I agree, but the same convention is for parsing OTLP parsing value. I would keep it as it is.

[reyang]

+1, echo from #2875 (comment)

[Kielek]

#2919 created

[pellared]

I left a few comments, but none of them is a blocker for me

[reyang]

LGTM.

[CodeBlanch]

LGTM