User notification client fixes

[tplaymeow]

• bc9ad36 Fixed delegate object deallocating. A similar solution is used in StoreKitClient.
  

  isowords/Sources/ComposableStoreKit/LiveKey.swift

  Lines 11 to 20 in bb0a73d

  	let stream = AsyncThrowingStream<ProductsResponse, Error> { continuation in
  	let request = SKProductsRequest(productIdentifiers: products)
  	let delegate = ProductRequest(continuation: continuation)
  	request.delegate = delegate
  	request.start()
  	continuation.onTermination = { [request = UncheckedSendable(request)] _ in
  	request.value.cancel()
  	_ = delegate
  	}
  	}

• 5e73c92 According to the documentation, delegate object must be assigned to UNUserNotificationCenter before app finishes launching.

[mbrandonw]

Great finds, thanks!