* WIP

* Allow `experimetnal_session_count` request serialization

* Extend `Plausible.Stats.Query` with `experimental_session_count` flag

* Add `FunWithFlags` actor implementation for `Site`

* Change the way sessions are retrieved

* Remove redundant test

* Format

* Update the test

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Co-authored-by: Uku Taht <uku.taht@gmail.com>