`PaymentPurpose` in `Event::PaymentClaimed` missing preimage when using custom `PaymentHash`

[Fedeparma74]

Description

When creating a BOLT11 invoice with a custom PaymentHash (instead of letting LDK generate one), the Event::PaymentClaimed event does not contain a PaymentPreimage inside the PaymentPurpose.

After calling ChannelManager::claim_funds() (where the preimage is provided by the application), LDK should then be aware of the preimage.

Expected Behavior

After calling claim_funds(preimage), the subsequent Event::PaymentClaimed should include PaymentPurpose::Bolt11InvoicePayment { payment_preimage: Some(preimage), .. } even when the invoice uses a custom PaymentHash.

Actual Behavior

payment_preimage is always None for Bolt11 payments with custom PaymentHash, even after the preimage has been supplied to LDK via claim_funds().

[chahat-101]

claim_funds(preimage) uses the preimage to fulfill HTLCs but does not persist it into inbound payment / invoice state.
Event::PaymentClaimed reconstructs PaymentPurpose from that state, which lacks a preimage for BOLT11 invoices created with a custom payment hash. Settlement succeeds, but payment_preimage is None.

If this is unintended, I’m happy to work on a fix that persists the preimage at claim time and includes it in PaymentClaimed. Please let me know if that approach makes sense.