[ getAlby/hub ] feat: allow self-paying invoices generated externally from LND (#1426)

* feat: allow self-paying invoices generated externally from LND

* chore: update self payment detection test to check for outgoing payment with same hash

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Co-authored-by: Roland Bewick

https://github.com/getAlby/hub/commit/74e54e64def32a6d53dd1e6ce3914329d39fee99