### Bugfixes
* `ErrorResponse`: don't add attribute errors to message if empty (#1844) via NachoSoto (@NachoSoto)
* Purchase cancellations: unify behavior between SK1 and SK2 (#1841) via NachoSoto (@NachoSoto)
* StoreKit 2: `PurchasesOrchestrator`: don't log "purchased product" if it was cancelled (#1840) via NachoSoto (@NachoSoto)
* `Backend`: fixed potential race conditions introduced by `OperationDispatcher.dispatchOnWorkerThread(withRandomDelay:)` (#1827) via NachoSoto (@NachoSoto)
* `DeviceCache`: `Sendable` conformance and fixed thread-safety (#1823) via NachoSoto (@NachoSoto)
* Directly send delegate customer info when delegate is set (always sends cached CustomerInfo value) (#1828) via Josh Holtz (@joshdholtz)
* `SystemInfo.finishTransactions`: made thread-safe (#1807) via NachoSoto (@NachoSoto)
* `Purchases.shared` and `Purchases.isConfigured` are now thread-safe (#1813) via NachoSoto (@NachoSoto)
* `PriceFormatterProvider: Sendable` conformance and fixed thread-safety (#1818) via NachoSoto (@NachoSoto)
* `StoreKitConfigTestCase.changeStorefront`: re-enabled on iOS 16 (#1811) via NachoSoto (@NachoSoto)

### Other Changes
* `DeviceCache`: no longer set cache timestamp before beginning request (#1839) via NachoSoto (@NachoSoto)
* `MagicWeatherSwiftUI`: updated to use `async` APIs (#1843) via NachoSoto (@NachoSoto)
* Release train (#1842) via Cesar de la Vega (@vegaro)
* Adds hotfixes section to RELEASING doc (#1837) via Cesar de la Vega (@vegaro)
* Update fastlane plugin (#1838) via Toni Rico (@tonidero)
* Update migration doc from didReceiveUpdatedCustomerInfo to receivedUpdatedCustomerInfo (#1836) via Josh Holtz (@joshdholtz)
* `PurchasesDelegate`: added test for latest cached customer info always being sent (#1830) via NachoSoto (@NachoSoto)
* `CallbackCache: Sendable` conformance (#1835) via NachoSoto (@NachoSoto)
* `CallbackCache`: simplified implementation using `Atomic` (#1834) via NachoSoto (@NachoSoto)
* `PurchasesLogInTests`: added test to verify `logIn` updates offerings cache (#1833) via NachoSoto (@NachoSoto)
* Created `PurchasesLoginTests` (#1832) via NachoSoto (@NachoSoto)
* `SwiftLint`: cleaned up output (#1821) via NachoSoto (@NachoSoto)
* Link to sdk reference (#1831) via aboedo (@aboedo)
* `Atomic: ExpressibleByBooleanLiteral` (#1822) via NachoSoto (@NachoSoto)
* `SwiftLint`: fixed build warning (#1820) via NachoSoto (@NachoSoto)
* Adds an approval job that will tag the release (#1815) via Cesar de la Vega (@vegaro)
* `Atomic: ExpressibleByNilLiteral` (#1804) via NachoSoto (@NachoSoto)
* `PurchasesAttributionDataTests`: fixed potential race condition in flaky test (#1805) via NachoSoto (@NachoSoto)
* Fixed warnings for unnecessary `try` (#1816) via NachoSoto (@NachoSoto)
* Moved `AttributionFetcherError` inside `AttributionFetcher` (#1808) via NachoSoto (@NachoSoto)
* Update documentation for presentCodeRedemptionSheet (#1817) via Joshua Liebowitz (@taquitos)
* `Dangerfile`: added "next_release" as supported label (#1810) via NachoSoto (@NachoSoto)
* PurchaseTester- Update Podfile.lock (#1814) via Joshua Liebowitz (@taquitos)
* Update to latest fastlane plugin (#1802) via Toni Rico (@tonidero)
* Clean up: moved `BackendIntegrationTests.xctestplan` to `TestPlans` folder (#1812) via NachoSoto (@NachoSoto)
* `SK2StoreProduct`: conditionally removed `@available` workaround (#1794) via NachoSoto (@NachoSoto)
* `SwiftLint`: fixed deprecation warning (#1809) via NachoSoto (@NachoSoto)
* Update gems (#1791) via Joshua Liebowitz (@taquitos)
* Replace usages of replace_in with replace_text_in_files action (#1803) via Toni Rico (@tonidero)

Fixes [CSDK-379] and #1041 (comment)

[CSDK-379]: https://revenuecats.atlassian.net/browse/CSDK-379?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

### Main changes:
- `Sendable` conformances to all types that are thread-safe
- `@unchecked Sendable` for types that the compiler can't enforce, but with documentation as to why
- Made classes that aren't mocked `final` (note that this doesn't change the API, because none of these were `open` to begin with)
- Made some classes thread-safe that weren't (like `DeviceCache`)

For the non-`final` `class`es, I've actually managed to compile the SDK with all of them as `final` and `Sendable`, to make sure that making them `@unchecked Sendable` didn't hide any other issues.

### Future improvements:
- https://twitter.com/nachosoto/status/1557139992056500224?s=21&t=arWdvEzTIFANBvwqQ0vPiA
- https://twitter.com/nachosoto/status/1557141944777592832?s=21&t=arWdvEzTIFANBvwqQ0vPiA
- https://twitter.com/nachosoto/status/1557143374922059776?s=21&t=arWdvEzTIFANBvwqQ0vPiA

### Depends on:
- #1794
- #1804
- #1806
- #1807
- #1808
- #1813
- #1822
- #1823
- #1824
- #1825
- #1826