feat: group by path endpoint and group members endpoint

[p-weisk]

Hi,
I came across the need to use the group by path and the group members endpoint. I mistakenly opened an issue for the group by path feature being missing from the all groups endpoint, since I overlooked the fact that it should be a separate endpoint.

Therefore, I created a pull request to implement the "GET /admin/realms/{realm}/groups/{group-id}/members" and the "GET /admin/realms/{realm}/group-by-path/{path}" endpoints.
Please let me know if there is anything I can improve on this pull request!

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 21 lines in your changes missing coverage. Please review.

Project coverage is 96.77%. Comparing base (3b6d4fe) to head (5ccb119).
Report is 30 commits behind head on main.

Files with missing lines	Patch %	Lines
src/Resource/Groups.php	0.00%	21 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #146      +/-   ##
==========================================
+ Coverage   95.81%   96.77%   +0.95%     
==========================================
  Files          36       27       -9     
  Lines         861      837      -24     
==========================================
- Hits          825      810      -15     
+ Misses         36       27       -9     

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[fschmtt]

Hey, thank you for contributing! 🎉

Generally LGTM, could you please fix the code styling issues (composer ecs:fix) and if you don't mind add unit tests for the new endpoints? 😄