[DOP-19838] Update Makefile & CONTRIBUTING.rst

[dolfinus]

Change Summary

• Sync Makefile with Data.Rentgen & Horizon implementations
• Rewrite CONTRIBUTING.rst according to changes above
• Running tests from local interpreter + using worker running inside docker container leads to issue. Conftest using address postgres://localhost:5433 to prepare source/target, and to create connections in database. But worker should access postgres://test-postges:5432, because it is running in the docker container within the same network. I've splitted up host+port for conftest & worker into different env variables, to solve this issue.

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.88%. Comparing base (59795ae) to head (816051d).
Report is 96 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #85      +/-   ##
===========================================
+ Coverage    92.86%   92.88%   +0.02%     
===========================================
  Files           84       84              
  Lines         2452     2461       +9     
  Branches       309      309              
===========================================
+ Hits          2277     2286       +9     
  Misses         122      122              
  Partials        53       53              

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