feat: NWC Funding source #2579 (#2631)

* feat: nwc funding source

* implement paid_invoices_stream, fix for unsettled invoices where settled_at is present but None

* cancel pending_payments_lookup_task on cleanup

* Rename subscription_timeout_task to timeout_task

* ensure preimage is not None

* Improve readability, return failed status on expiration in get_payment_status, ensure result_type is checked after error (some implementations might not set a result_type on error)

* fetch account info when possible

* workaround possible race condition on some nwc service providers, improve performance of fallback by using payment_hash from bolt11 invoice

* fundle

* make format

* fix formatting

* fix C901 `_on_message` is too complex (21 > 16)

* format

* fix lint

* format

* fix tests/wallets/test_nwc_wallets.py:80:11: C901 `run` is too complex (17 > 16)

* fix padding

* fix documentation for _verify_event method

* refactoring and fixes

* Split NWCWallet - NWCConnection

* refactor class methods into helpers

* update bundle

* format

* catch NWCError failure codes

* format and fix

* chore: bundle

* add example

* typos

---------

Co-authored-by: Riccardo Balbo <riccardo0blb@gmail.com>
Co-authored-by: benarc <ben@arc.wales>
Co-authored-by: Pavol Rusnak <pavol@rusnak.io>

docs/guide/wallets.md

@@ -124,3 +124,12 @@ A Greenlight invite code or Greenlight partner certificate/key can be used to re
 ### Cliche Wallet
 
 - `CLICHE_ENDPOINT`: ws://127.0.0.1:12000
+
+### Nostr Wallet Connect (NWC)
+
+To use NWC as funding source in LNbits you'll need a pairing URL (also known as pairing secret) from a NWC service provider. You can find a list of providers [here](https://github.com/getAlby/awesome-nwc?tab=readme-ov-file#nwc-wallets).
+
+You can configure Nostr Wallet Connect in the admin ui or using the following environment variables:
+
+- `LNBITS_BACKEND_WALLET_CLASS`: **NWCWallet**
+- `NWC_PAIRING_URL`: **nostr+walletconnect://...your...pairing...secret...**