[DOP-20893] Add <role> attribute to /v1/groups/:id response

[IlyasDevelopment]

Change Summary

GET /v1/groups/:id endpoint changed the response format from:

{
  “id": 123,
  “name": "abc",
  “description": “cde”
}

to

{
  “data": {
    “id": 123,
    “name": "abc",
    “description": “cde”
  }, 
  “role”: “DEVELOPER”
}

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 92.81%. Comparing base (b0d4560) to head (59f8d53).
Report is 80 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #109      +/-   ##
===========================================
+ Coverage    92.79%   92.81%   +0.02%     
===========================================
  Files           98       98              
  Lines         2803     2811       +8     
  Branches       228      229       +1     
===========================================
+ Hits          2601     2609       +8     
  Misses         150      150              
  Partials        52       52              

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