Clairview

1. Add support for returning payloads of matched feature flags

Changes:

1. Add support for feature flag variant overrides with local evaluation

Changes:

1. Fixes issues with date comparison.

Changes:

1. Feature flags local evaluation now supports date property filters as well. Accepts both strings and datetime objects.

Changes:

1. Feature flag defaults have been removed
2. Setup logging only when debug mode is enabled.

- Make poll_interval configurable
- Add `send_feature_flag_events` parameter to feature flag calls, which determine whether the `$feature_flag_called` event should be sent or not.
- Add `only_evaluate_locally` parameter to feature flag calls, which determines whether the feature flag should only be evaluated locally or not.