feat: support list users

[rhamzeh]

Description

References

• Parent Epic: Support ListUsers endpoint sdk-generator#329

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 17.79279% with 730 lines in your changes are missing coverage. Please review.

Project coverage is 22.51%. Comparing base (d637093) to head (17c79da).

Files	Patch %	Lines
api_open_fga.go	23.39%	121 Missing and 10 partials ⚠️
model_list_users_request.go	13.11%	105 Missing and 1 partial ⚠️
model_unprocessable_content_message_response.go	0.00%	70 Missing ⚠️
model_object_or_userset.go	0.00%	66 Missing ⚠️
model_user.go	22.89%	60 Missing and 4 partials ⚠️
model_userset_user.go	14.08%	60 Missing and 1 partial ⚠️
model_user_type_filter.go	16.12%	51 Missing and 1 partial ⚠️
model_fga_object.go	15.51%	48 Missing and 1 partial ⚠️
model_list_users_response.go	15.51%	48 Missing and 1 partial ⚠️
model_unprocessable_content_error_code.go	0.00%	41 Missing ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #81      +/-   ##
==========================================
- Coverage   22.98%   22.51%   -0.48%     
==========================================
  Files          84       94      +10     
  Lines        8870     9758     +888     
==========================================
+ Hits         2039     2197     +158     
- Misses       6599     7308     +709     
- Partials      232      253      +21     

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