[MINOR] chore: migrate coverage upload to qlty

[ayush-eb]

Migrate Coverage Upload to QLTY

Summary

This PR migrates coverage reporting to QLTY Cloud by adding XML coverage report generation and QLTY upload steps. Changes were made by AI and may contain mistakes - please review carefully.

Changes Made

1. Added XML coverage report generation in .travis.yml:

   • Added --cov-report xml to all pytest commands
   • This generates coverage.xml (Cobertura format) alongside the existing terminal report

2. Added QLTY coverage upload to .travis.yml:

   • Installs QLTY CLI in after_script section for all test jobs
   • Uploads coverage.xml to QLTY when running on master branch
   • Uses || true to prevent CI failures if upload fails

Setup Required

1. Set QLTY_COVERAGE_TOKEN in Travis CI environment variables:

   • Go to: https://qlty.sh/gh/eventbrite/pymetrics/settings/coverage/reports
   • Copy the coverage token
   • Add it as QLTY_COVERAGE_TOKEN in Travis CI project settings

2. Verify coverage upload:

   • After merging, check that coverage appears in QLTY dashboard
   • Coverage upload only runs on master branch (default branch requirement)

Testing

• Coverage generation tested via existing pytest configuration
• QLTY upload will be validated in CI after token is configured
• Note: Travis CI is deprecated - consider migrating to GitHub Actions or CircleCI in the future

Coverage Details

• Format: Cobertura XML (coverage.xml)
• Location: Repository root
• Generated by: pytest with --cov-report xml flag
• Upload trigger: Push to master branch