This bug seems to be Electrum-specific. The fix is to check the
proposed changes against the current state of the database. Ensure
newly suggested indexes are not smaller than indexes already in
database.
Changes:
* Check index updates before they are applied to database during
Electrum Blockchain sync (Thank you @rajarshimaitra for providing
an elegant solution).
Tests added:
* bdk_blockchain_tests!::test_sync_address_index_should_not_decrement
* bdk_blockchain_tests!::test_sync_address_index_should_increment
These tests ensure there will be no unexpected address reuse when
grabbing a new address via `Wallet::get_address` with `AddressIndex::New`.
Other changes:
* Tweak `rpc.rs` so that clippy is happy.
A `is_spent` field is added to LocalUtxo; when a txo is spent we set
this field to true instead of deleting the entire utxo from the
database.
This allows us to create txs double-spending txs already in blockchain.
Listunspent won't return spent utxos, effectively excluding them from the
coin selection and balance calculation
