Closes #15 - Replaced requests with httpx

[petruki]

This pull request modernizes the HTTP client used in the codebase by migrating from requests to httpx and updates the test suite to use pytest-httpx instead of responses. It also upgrades several GitHub Actions to their latest major versions and refreshes dependencies in the Pipfile. Additionally, a new contributing section is added to the README.md. The most important changes are grouped below:

Migration to httpx and test refactoring:

• Replaced all usage of requests with httpx in switcher_client/lib/remote.py, introducing connection pooling and HTTP/2 support via a shared httpx.Client. All internal HTTP methods are now private and use the new client. [1] [2] [3] [4] [5]
• Refactored tests to use pytest-httpx instead of responses, updating all test helpers and test cases in tests/test_client_load_snapshot_remote.py and tests/test_switcher_remote.py to use httpx_mock for mocking HTTP requests. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]

Dependency and workflow updates:

• Updated Pipfile dependencies: replaced requests with httpx[http2], upgraded pytest, pytest-cov, and switched to pytest-httpx for HTTP mocking in tests.
• Upgraded GitHub Actions in all workflow files (.github/workflows/*.yml) to use actions/checkout@v5 and actions/setup-python@v6 for improved reliability and security. [1] [2] [3] [4] [5]

Documentation:

• Added a new "Contributing" section to README.md with clear instructions for new contributors and project requirements.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud