### Changes:
- `InternalAPI` is now `Sendable` to deal with new compilation error
- `PaywallEventStoreType` is now `Sendable`
- Extracted `SK2BeginRefundRequestHelperType` to make
`SK2BeginRefundRequestHelper` `Sendable`
- Updated `MockSK2BeginRefundRequestHelper` to be thread-safe and
`Sendable`
- Fixed compilation error in `DebugContentViews`
- Fixed compilation error in `DebugViewModel`
- Fixed compilation error in `StoreMessagesHelper`
Fixes https://github.com/RevenueCat/purchases-capacitor/issues/100 and
https://app.circleci.com/pipelines/github/RevenueCat/purchases-ios/14093/workflows/b3f8d001-6f39-40db-a5c5-00fc37d0211e/jobs/105838
```
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 ??? 0x0 ???
1 libswiftCore.dylib 0x18f9b8cf8 swift_getSingletonMetadata + 956
2 RevenueCat 0x107f42de4 type metadata accessor for DebugViewModel + 64
3 libobjc.A.dylib 0x18017d938 realizeClassMaybeSwiftMaybeRelock(objc_class*, mutex_tt<false>&, bool) + 116
4 libobjc.A.dylib 0x180184eb0 realizeAllClasses() + 168
5 libobjc.A.dylib 0x180187b3c objc_copyClassList + 36
6 XCTestCore 0x10532fcb0 +[XCTestCase(RuntimeUtilities) _allSubclasses] + 36
7 XCTestCore 0x10532fdb8 +[XCTestCase(RuntimeUtilities) allSubclasses] + 16
```
Both `XCTest` (to load tests at runtime) and `Capacitor` use
`objc_getClassList`. That's broken before iOS 16 and will try to load
the metadata for `DebugViewModel` even though it's not `@available`.
A similar issue has been reported before:
https://openradar.appspot.com/radar?id=4970535809187840 /
https://github.com/apple/swift/issues/58099
This adds a layer of indirection so loading `DebugViewModel` at runtime
doesn't require the metadata for `NavigationPath`.
### Context:
`#if os(iOS)` no longer evaluates to `true` when compiling for
`visionOS`
Which means we need `|| os(xrOS)`.
But to support older Xcode we need `#if swift(>=5.9) && os(xrOS)`.
But, fun fact, short-circuiting doesn’t work in `Xcode 13`.
And we still need that to run iOS <15 tests (`FB12223404` /
`FB12805891`)
💩
This works around that by defining our own `VISION_OS` flag.
### Changes:
- Added `VISION_OS` compile time flag to determine SDK
- Replaced `#if os(xrOS)` with `#if VISION_OS`
- Added flag to `Package.swift` (thanks @neonichu for helping with this)
### Changes:
- Exposed `internal`-only `Purchases.cachePresentedOfferingIdentifier`
- Changed `SwiftUI` extensions to `static` methods: this is required to
be able to call an instance method on them
- Added integration test to verify this offering identifier is used
Technically this is an API change, but these APIs are implicitly beta
because they're only available in Xcode 15 beta.
NachoSoto