feat: added Client.watch_snapshot for real-time snapshot monitoring

[petruki]

This pull request introduces snapshot file monitoring to the Switcher client, allowing the system to automatically detect and handle changes to the snapshot file in real time. The main changes include implementing the snapshot watcher logic, integrating it into the client API, updating documentation and playground use cases, and adding comprehensive tests for the new feature.

Snapshot monitoring feature:

• Added the SnapshotWatcher class to switcher_client/lib/snapshot_watcher.py, which uses a background thread to poll the snapshot file for changes and reloads the snapshot when modifications are detected. It invokes success or error callbacks as appropriate.
• Integrated snapshot monitoring into the Client API by adding watch_snapshot and unwatch_snapshot methods, updating resource cleanup logic, and wiring up the watcher instance. [1] [2] [3] [4]

Documentation and playground updates:

• Updated the README.md to document the new snapshot monitoring feature and provide usage examples.
• Refactored playground use case functions and added a new uc_watch_snapshot function to demonstrate snapshot monitoring in tests/playground/index.py. [1] [2] [3] [4] [5] [6]

Testing:

• Added a new test suite tests/test_client_watch_snapshot.py to verify snapshot monitoring behavior, error handling for missing or malformed snapshot files, and correct callback invocation.
• Added a malformed snapshot fixture for testing error handling.

[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