4.0.0-alpha.2

The gist of the big breaking changes are now done for the 4.x branch. Here are the major changes in this pre-release:

• ✅ Replace react-final-form with react-hook-form (#7087)
• ✅ Remove Resource initialization, Store Resource definitions in Context rather than in store (#7051)
• ✅ Remove deprecated sort prop in <DataGridHeaderCell> (#7065)
• ✅ Rename currentSort to sort (#7076)
• ✅ Change the Record TypeScript name to RaRecord (#7078)
• ✅ Put <Notification> component in the <AdminUI> to avoid gotchas when overriding the layout, and remove notifications from Redux store ( #7082)
• ✅ Remove basePath (#7100)
• ✅ Allow to pass custom params to each dataProvider hooks (#7116)
• ✅ Add support for partial pagination (i.e. no total) (#7120)
• ✅ Remove TestContext (AdminContext does the trick) and ra-test (#7148)

We've also done a huge work on the documentation. The UPGRADE guide is complete but will need a rewrite to make it easier to follow.

This release represents 48 pull requests and more than 500 commits since the previous alpha, it's a huge work. Thanks to all the contributors to this version, especially @djhi, @fzaninotto, and @WiXSL!

If you can, please test this pre-release and report regressions that aren't already identified in the upgrade guide. We plan to release one more alpha before the beta version.