test(HRIS): add test suite for "create employee" flow

[niklashigi]

Note

Adds coverage for the employee form-based create flow.

• New tests/test_employee_form_flow.py with two tests: get_employee_form (GET \v1\hris\employees\form) and create_employee_with_form (POST \v1\hris\employees\form)
• Validates returned form properties (e.g., firstName, keyNumbers, nested workLocation.site) and confirms empty warnings
• Verifies successful creation response fields (id, remote_id, prehire.remote_id) and snapshots the serialized request properties payload
• Uses MockContext and inline_snapshot for endpoint mocking and request body assertion

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