otelsarama: Add WithAllowRootSpanStart option

[keitwb]

This will allow the parent app to control whether a span will be created based on whether the message contains injected context.

The default is 'true' which will preserve the original behavior.

[pellared]

@kweitb Generally the code looks OK but I am not sure it would not be better to use Sampler which filter's out span's without a parent. Have you checked Sampler interface and existing samplers?

[codecov[bot]]

Codecov Report

Merging #770 (0c1c8de) into main (13d72c9) will increase coverage by 0.0%. The diff coverage is 95.0%.

@@          Coverage Diff          @@
##            main    #770   +/-   ##
=====================================
  Coverage   78.4%   78.4%           
=====================================
  Files         62      62           
  Lines       2737    2747   +10     
=====================================
+ Hits        2146    2156   +10     
  Misses       456     456           
  Partials     135     135           

Impacted Files	Coverage Δ
...n/github.com/Shopify/sarama/otelsarama/producer.go	95.2% <93.3%> (+0.3%)	:arrow_up:
...ion/github.com/Shopify/sarama/otelsarama/option.go	100.0% <100.0%> (ø)

[keitwb]

@kweitb Generally the code looks OK but I am not sure it would not be better to use Sampler which filter's out span's without a parent. Have you checked Sampler interface and existing samplers?

That sounds promising but it's not clear to me how to do this.

[pellared]

@keitwb Do you still want/need this? Are you planning to update the PR? Should the PR be closed?

[pellared]

otelsarama is deprecated. I am closing this PR. More info: https://github.com/open-telemetry/opentelemetry-go-contrib/issues/4091