Implement `responses` library for HTTP Layer Integration Testing

[avelino]

We should implement the responses library for HTTP integration testing in our SDK for the following reasons:

1. Reliable HTTP Mocking: responses allows us to mock HTTP requests without making actual API calls, ensuring consistent test behavior regardless of API availability. ref
2. Test Scenarios Coverage:

• Mock different HTTP response codes
• Simulate various API responses
• Test error handling scenarios
• Validate request parameters and headers ref

3. Test Performance: By eliminating actual network calls, tests run faster and don't depend on external services, providing shorter feedback loops during development. ref
4. Automated Response Handling: The library supports dynamic response generation based on request parameters, enabling comprehensive testing of different API scenarios. ref