Links attached to payments not shown anymore (successAction field missing)

[al-munazzim]

Cross-posted from blinkbitcoin/blink-mobile#3212
Originally reported by @MichaelAntonFischer

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Describe the bug
For a while, links that are attached to invoice paid from Blink are not shown anymore. So functions like the LNpos offline mode don't work.

To Reproduce
Steps to reproduce the behavior:

1. Create invoice with LNpos
2. Pay
3. No link

Smartphone (please complete the following information):

• Device: iPhone 14

Additional context
Wallet of Satoshi and others work fine. See here:

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Technical Analysis:

This issue requires a backend change. The mobile app frontend code is fully implemented (see SuccessActionSection component in transaction-detail-screen.tsx), but the backend GraphQL schema is missing the successAction field on the SettlementViaLn type.

Root Cause: The SettlementViaLn type in the GraphQL schema only has paymentSecret and preImage fields - it doesn't include successAction to expose the LUD-09 success action data from LNURL payments.

Required Change: Add successAction field to SettlementViaLn GraphQL type with the following structure:

type SuccessAction {
  tag: String
  message: String
  url: String
  description: String
  ciphertext: String
  iv: String
}

Related: Mobile PR prep commits exist for this feature (see blink-mobile#3463).

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• Original: Links attached to payments not shown anymore blink-mobile#3212
• Reporter: @MichaelAntonFischer