Add Users.read endpoint for Terraform Cloud User API

[TanyaSingh369-svg]

Description

Summary

This PR adds support for the Terraform Cloud User API in the Python SDK.

Changes

• Implemented Users.read(user_id) resource based on the User API endpoint.
• Added input validation using valid_string_id.
• Integrated the Users service into the TFE client.
• Parsed API responses into the existing User model.
• Added unit tests for response parsing and invalid ID validation.

Testing

• Added tests in tests/units/test_user.py.
• Verified the new tests pass locally.
• Verified the full test suite passes successfully.

Testing Plan

1. Run the new Users resource tests:
   PYTHONPATH=. pytest tests/units/test_user.py -v

   Output:

   • tests/units/test_user.py::TestUsers::test_read_user PASSED
   • tests/units/test_user.py::TestUsers::test_read_user_invalid_id PASSED

2. Run the full unit test suite:
   PYTHONPATH=. pytest

Output:

3. Verified the following behavior:
   • Users.read(user_id) sends a GET request to /api/v2/users/{user_id}
   • the API response is parsed into the existing User model
   • invalid user_id input triggers validation failure

[TanyaSingh369-svg]

I raised a clean replacement PR with only the User API related changes, so I’m closing this one to avoid unrelated diff changes.