`Wallet` stores the descriptors' checksum in the database for safety.
Previously, the checksum used was a checksum of a descriptor that
already had a checksum.
This PR allows for backward-compatibility of databases created with this
bug.
If `exclude_hash` is set, we split the input data, and if a checksum
already existed within the original data, we check the calculated
checksum against the original checksum.
Additionally, the implementation of `IntoWalletDescriptor` for `&str`
has been refactored for clarity.
`get_checksum_bytes` returns a descriptor checksum as `[u8; 8]` instead
of `String`, potentially improving performance and memory usage.
In addition to this, since descriptors only use charaters that fit
within a UTF-8 8-bit code unit, there is no need to use the `char` type
(which is 4 bytes). This can also potentially bring in some performance
and memory-usage benefits.
This allows the signer to know the signing context precisely without
relying on heuristics on the psbt fields.
Due to the context being static, we still have to look at the PSBT when
producing taproot signatures to determine the set of leaf hashes that
the key can sign for.
Although somewhat convenient to have, coupling the Wallet with
the blockchain trait causes development friction and complexity.
What if sometimes the wallet is "offline" (no access to the blockchain)
but sometimes its online?
The only thing the Wallet needs the blockchain for is to sync.
But not all applications will even use the sync method and the sync
method doesn't require the full blockchain functionality.
So we instead pass the blockchain in when we want to sync.
- To further reduce the coupling with blockchain I removed the get_height call from `new` and just use the height of the
last sync in the database.
- I split up the blockchain trait a bit into subtraits.
Idiomatic Rust uses lowercase for acronyms for all characters after the
first e.g. `std::net::TcpStream`. PSBT (Partially Signed Bitcoin
Transaction) should be rendered `Psbt` in Rust code if we want to write
idiomatic Rust.
Use `Psbt` instead of `PSBT` when aliasing the import of
`PartiallySignedTransaction` from `bitcoin` library.
