Split it based on whether the purpose is “editing” or “sharing”. If
we’re editing, it generally means we have full access to contacts, and
that we’ve checked which of the contacts are registered on Signal. If
we’re “sharing”, we don’t care whether or not they’re registered.
If we’re “sharing”, we check whether or not we’ve prompted for the
contacts permission yet. If not, we’ll show the prompt.
If we’re “editing”, we assume we’ve already prompted (which is already
the case today), so `.notDetermined` isn’t a possible state.
Other things to note:
- The `supportsContactEditing` was always true, so it’s been removed.
- The error when contacts access isn’t allowed is now shown more
consistently. Previously, it was sometimes shown in response to
initializing a view controller.
- Some RecipientPickerViewController code was moved from Obj-C to Swift.
This is probably useful on its own, but it’ll also make it easier to
build some new UI in subsequent commits.