Added SpanProcessor OnEnding callback

[JonasKunz]

Implementation for the spec change https://github.com/open-telemetry/opentelemetry-specification/pull/4024.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 97.36842% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.01%. Comparing base (3e8092d) to head (80aa059). Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
.../main/java/io/opentelemetry/sdk/trace/SdkSpan.java	96.42%	0 Missing and 1 partial :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6367      +/-   ##
============================================
- Coverage     90.05%   90.01%   -0.05%     
- Complexity     6276     6330      +54     
============================================
  Files           697      703       +6     
  Lines         18949    19086     +137     
  Branches       1858     1881      +23     
============================================
+ Hits          17065    17180     +115     
- Misses         1312     1331      +19     
- Partials        572      575       +3     

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[jkwatson]

I approve of putting this in a separate interface. But, we should provide documentation on how someone could use this, as well.

[JonasKunz]

But, we should provide documentation on how someone could use this, as well.

What do you think would be the best place for this? Just a javadoc in ExtendedSpanProcessor or do we have some markdown files somewhere where this would fit in nicely?

[jack-berg]

What do you think would be the best place for this? Just a javadoc in ExtendedSpanProcessor or do we have some markdown files somewhere where this would fit in nicely?

I think the ideal way to do this is a unit test. Let's add an ExtendedSpanProcessorUsageTest akin to what we do in the api incubator. No obvious place to link to the usage test at the moment, but let's start by at least demonstrating its usage in clear terms.