fix(#1960): make calculation of the DRep voting power on the backend

[MSzalowski]

List of changes

• make calculation of the DRep voting power on the backend

Checklist

• related issue
• [x] My changes generate no new warnings
• [x] My code follows the style guidelines of this project
• [ ] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the changelog
• [ ] I have added tests that prove my fix is effective or that my feature works

[github-actions[bot]]

:white_check_mark: All checks succeeded

[github-actions[bot]]

:white_check_mark: All checks succeeded

[github-actions[bot]]

:white_check_mark: All checks succeeded

[github-actions[bot]]

@MSzalowski This PR is in the tag: develop-1d96a734582b54be94c1658d30e1637eed77ca5e , for govtool-metadata-validation service

[github-actions[bot]]

@MSzalowski This PR is in the tag: develop-1d96a734582b54be94c1658d30e1637eed77ca5e , for govtool-frontend service