introductory offer in JWSTransactionDecodedPayload object

ResponseBody.Latest_receipt_info object have a is_trial_period member， what is the same meaning member in JWSTransactionDecodedPayload object?

Within JWSTransactionDecodedPayload is is_trial_period, and that has the value of true, or of false.

True indicates within the trial period. False indicates not:

is_trial_period | Apple Developer Documentation

For introductory offers:

Implementing introductory offers in your app | Apple Developer Documentation

For promotional offers:

https://help.apple.com/app-store-connect/#/dev16dfca448

For using promo codes:

Request and manage promo codes - Offer promo codes - App Store Connect - Help - Apple Developer

I’d probably start with skimming the whole document:

Enabling App Store Server Notifications | Apple Developer Documentation

There was WWDC videos (and links) here, as well:

What’s new in App Store server APIs - WWDC23 - Videos - Apple Developer

Expanding automation with the App Store Connect API - WWDC20 - Videos - Apple Developer

Apple Developer also has one-on-one consultations for design and for app analytics available:

Meet with Apple Experts - Apple Developer

Start here for what Apple documents on the App Store notification API: offerType | Apple Developer Documentation