fix: use default endpoint for endpoint when provided empty string

[joonas]

Changes

According to the WithExporterConfig docs, passing an empty string towith_endpoint should result in the default endpoint being used, however that's not currently what happens.

This change adds an additional check to make sure that the provided endpoint is not an empty string, and if it is, then it'll fall back to using the default endpoint instead.

As an aside, I considered changing the WithExportConfig implementation of with_endpoint to do this check, and if that's the preferred route to go, I'm happy to switch these changes over to there instead.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.2%. Comparing base (200885a) to head (3ecf829).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3000   +/-   ##
=====================================
  Coverage   81.2%   81.2%           
=====================================
  Files        126     126           
  Lines      24839   24855   +16     
=====================================
+ Hits       20173   20189   +16     
  Misses      4666    4666           

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