This will help specific deployments that need to do something custom here such
as redirect the user or call some API after Element has logged out and cleared
storage.
The "remember my selection" option wasn't working because the `missing` set still included the approved permission. Solution: remove it from `missing`.
The customisation point is to allow forks to change which widgets get which additional capabilities dependent on their own rules.
This adds various customisations point in the app for security related
decisions. By default, these do nothing, but would be customised at the
app level via module replacement (so that no changes are needed here in the
SDK).
Fixes https://github.com/vector-im/element-web/issues/15350
