[lib/native] lift auto join community handler to lib

Summary:
We are going to want to use the auto join community handler in web. Before we can do that though, we need to lift the auto join community handler into lib. One thing to note is that there is a difference in calendarQuery between web and native, so we need to separate this logic for each platform.

Depends on D12714

Test Plan: flow + confirmed there were no regressions

Reviewers: ashoat, inka

Reviewed By: ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12716