<!-- Release notes generated using configuration in .github/release.yml at main -->
Faster cohorts detection, property tests, and a beta quality implementation of scans (`nancumsum`, `ffill`, `bfill`)
What's Changed
* Property tests with hypothesis by dcherian in https://github.com/xarray-contrib/flox/pull/348
* Add scans by dcherian in https://github.com/xarray-contrib/flox/pull/370
* Optimize for-loop merging of cohorts. by dcherian in https://github.com/xarray-contrib/flox/pull/378
**Full Changelog**: https://github.com/xarray-contrib/flox/compare/v0.9.8...v0.9.9