is this spam?

So many red flags there. Its totally a scam.

Just for starters, there is no such thing as "Apple Pay Pre Authorization" and Apple Pay is not used in the App Store at all.

The fact they mix events together for a charge and some apple pay activation, and the fact it was sent as an iMessage.

Apple never sends iMessages for App Store events. Also, in general they absolutely never warn of "suspicious activity"

They'll just issue a message for a login to your account, but, I have never seen a message for a random purchase.

And never a single message for more than one event or issue.

So, yes, this is very much a bold faced scam.

Ignore it entirely. You can delete it, and block the sender.

Yes, it is a Scam attempt. Do not interact with the message or the sender.

Yes, it’s a scam.

The grammar errors are a big clue.