add codecov token and fail on error

[jpinsonneau]

Attempt to fix dependabot failures
https://github.com/netobserv/network-observability-cli/actions/runs/8659316614/job/23869357082?pr=23

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 31.25%. Comparing base (f58b119) to head (d312e47).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##            main      #28       +/-   ##
==========================================
+ Coverage   0.00%   31.25%   +31.25%     
==========================================
  Files          5        5               
  Lines        898      944       +46     
==========================================
+ Hits           0      295      +295     
+ Misses       898      629      -269     
- Partials       0       20       +20     

Flag	Coverage Δ
unittests	31.25% <ø> (+31.25%)	⬆️

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[openshift-ci]

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