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.
Clippy emits:
warning: Question mark operator is useless here
No need to use the `?` operator inside an `Ok()` statement when
returning, just return directly.
While technically it's not required since there are no timelocks inside,
it's still less confusing for the end user if we allow this instead of
failing like we do currently.
The `TooManyItemsSelected` error has been removed, since it's not technically an
error but potentailly more of an "over-constraint" over a tx: for instance,
given a `thresh(3,pk(a),pk(b),older(10),older(20))` descriptor one could create
a spending tx with the `[0,1,2]` items that would only be spendable after `10`
blocks, or a tx with the `[0,2,3]` items that would be spendable after `20`.
In this case specifying more items than the threshold would create a tx with
the maximum constraint possible, in this case the `20` blocks. This is not
necessarily an error, so we should allow it without failing.
