Apple Wallet is usually a quick double-press away on the iPhone or Apple Watch to pull up payment cards or travel cards. In a very few places you can already add drivers licenses and IDs, but beyond that, not much else (I did note Discovery Health in South Africa does a quick add of your health insurance as a digital card too).
Wallet Creator is an app that allows you to easy scan QR codes and manually add these with some details to Apple Wallet, no matter what region you are in. It works ideally with a QR code being scanned, because although it can also scan a photo or image, this ends up as a tiny thumbnail only, as far as I can see.
Just a pity my vaccination card has no QR code, and the imported image is too small to read.
See How to manually add your vaccination certificate to Apple Wallet
Whenever you’re requested to show your vaccination certificate, you’re a double side click away from entering your favorite spot.