Features
* Implement "sample_rate" property for transactions and spans, and propagate through tracestate (891)
* Add support for callbacks on config changes (912)
* Override `sys.excepthook` to catch all exceptions (943)
* Implement `log_level` config (supports central config) (946)
* Implement `transaction_ignore_urls` config (supports central config) (923)
* Add public API to retrieve trace parent header (956)
* Added support for cgroup memory metrics (846)
Bug fixes
* Fix to collect the whole query body in `elasticsearch-py` (940)
* Fix for GraphQL transaction naming (881)
* Ensure that query string max length is maintained after sanitization (968)
* Adapted kubernetes kubepod regex for detecting kubernetes metadata (958)
* Updated Starlette integration to use the route as transaction name if possible (957)