sqldb: add queries for deleting a payment and attempts

sqldb/sqlc/queries/payments.sql

@@ -151,3 +151,13 @@ FROM payment_hop_custom_records l
 WHERE l.hop_id IN (sqlc.slice('hop_ids')/*SLICE:hop_ids*/)
 ORDER BY l.hop_id ASC, l.key ASC;
 
+
+-- name: DeletePayment :exec
+DELETE FROM payments WHERE id = $1;
+
+-- name: DeleteFailedAttempts :exec
+-- Delete all failed HTLC attempts for the given payment. Resolution type 2
+-- indicates a failed attempt.
+DELETE FROM payment_htlc_attempts WHERE payment_id = $1 AND attempt_index IN (
+    SELECT attempt_index FROM payment_htlc_attempt_resolutions WHERE resolution_type = 2
+);