feat!: Rework sqlite, changesets, persistence and wallet-construction

Rework sqlite: Instead of only supported one schema (defined in
`bdk_sqlite`), we have a schema per changeset type for more flexiblity.

* rm `bdk_sqlite` crate (as we don't need `bdk_sqlite::Store` anymore).
* add `sqlite` feature on `bdk_chain` which adds methods on each
  changeset type for initializing tables, loading the changeset and
  writing.

Rework changesets: Some callers may want to use `KeychainTxOutIndex`
where `K` may change per descriptor on every run. So we only want to
persist the last revealed indices by `DescriptorId` (which uniquely-ish
identifies the descriptor).

* rm `keychain_added` field from `keychain_txout`'s changeset.
* Add `keychain_added` to `CombinedChangeSet` (which is renamed to
  `WalletChangeSet`).

Rework persistence: add back some safety and convenience when persisting
our types. Working with changeset directly (as we were doing before) can
be cumbersome.

* Intoduce `struct Persisted<T>` which wraps a type `T` which stores
  staged changes to it. This adds safety when creating and or loading
  `T` from db.
* `struct Persisted<T>` methods, `create`, `load` and `persist`, are
  avaliable if `trait PersistWith<Db>` is implemented for `T`. `Db`
  represents the database connection and `PersistWith` should be
  implemented per database-type.
* For async, we have `trait PersistedAsyncWith<Db>`.
* `Wallet` has impls of `PersistedWith<rusqlite::Connection>`,
  `PersistedWith<rusqlite::Transaction>` and
  `PersistedWith<bdk_file_store::Store>` by default.

Rework wallet-construction: Before, we had multiple methods for loading
and creating with different input-counts so it would be unwieldly to add
more parameters in the future. This also makes it difficult to impl
`PersistWith` (which has a single method for `load` that takes in
`PersistWith::LoadParams` and a single method for `create` that takes in
`PersistWith::CreateParams`).

* Introduce a builder pattern when constructing a `Wallet`. For loading
  from persistence or `ChangeSet`, we have `LoadParams`. For creating a
  new wallet, we have `CreateParams`.

example-crates/wallet_esplora_blocking/src/main.rs

@@ -1,52 +1,56 @@
-const DB_MAGIC: &str = "bdk_wallet_esplora_example";
-const SEND_AMOUNT: Amount = Amount::from_sat(1000);
-const STOP_GAP: usize = 5;
-const PARALLEL_REQUESTS: usize = 1;
-
-use std::{collections::BTreeSet, io::Write, str::FromStr};
+use std::{collections::BTreeSet, io::Write};
 
 use bdk_esplora::{esplora_client, EsploraExt};
 use bdk_file_store::Store;
 use bdk_wallet::{
-    bitcoin::{Address, Amount, Network},
-    KeychainKind, SignOptions, Wallet,
+    bitcoin::{Amount, Network},
+    wallet::{CreateParams, LoadParams},
+    KeychainKind, SignOptions,
 };
 
-fn main() -> Result<(), anyhow::Error> {
-    let db_path = std::env::temp_dir().join("bdk-esplora-example");
-    let mut db =
-        Store::<bdk_wallet::wallet::ChangeSet>::open_or_create_new(DB_MAGIC.as_bytes(), db_path)?;
-    let external_descriptor = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/1'/0'/0/*)";
-    let internal_descriptor = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/1'/0'/1/*)";
-    let changeset = db.aggregate_changesets()?;
+const DB_MAGIC: &str = "bdk_wallet_esplora_example";
+const DB_PATH: &str = "bdk-example-esplora-blocking.db";
+const SEND_AMOUNT: Amount = Amount::from_sat(5000);
+const STOP_GAP: usize = 5;
+const PARALLEL_REQUESTS: usize = 5;
 
-    let mut wallet = Wallet::new_or_load(
-        external_descriptor,
-        internal_descriptor,
-        changeset,
-        Network::Testnet,
-    )?;
+const NETWORK: Network = Network::Signet;
+const EXTERNAL_DESC: &str = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/1'/0'/0/*)";
+const INTERNAL_DESC: &str = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/1'/0'/1/*)";
+const ESPLORA_URL: &str = "http://signet.bitcoindevkit.net";
+
+fn main() -> Result<(), anyhow::Error> {
+    let mut db =
+        Store::<bdk_wallet::wallet::ChangeSet>::open_or_create_new(DB_MAGIC.as_bytes(), DB_PATH)?;
+
+    let load_params = LoadParams::with_descriptors(EXTERNAL_DESC, INTERNAL_DESC, NETWORK)?;
+    let create_params = CreateParams::new(EXTERNAL_DESC, INTERNAL_DESC, NETWORK)?;
+
+    let mut wallet = match load_params.load_wallet(&mut db)? {
+        Some(wallet) => wallet,
+        None => create_params.create_wallet(&mut db)?,
+    };
 
     let address = wallet.next_unused_address(KeychainKind::External);
-    if let Some(changeset) = wallet.take_staged() {
-        db.append_changeset(&changeset)?;
-    }
-    println!("Generated Address: {}", address);
+    wallet.persist(&mut db)?;
+    println!(
+        "Next unused address: ({}) {}",
+        address.index, address.address
+    );
 
     let balance = wallet.balance();
     println!("Wallet balance before syncing: {} sats", balance.total());
 
     print!("Syncing...");
-    let client =
-        esplora_client::Builder::new("https://blockstream.info/testnet/api").build_blocking();
+    let client = esplora_client::Builder::new(ESPLORA_URL).build_blocking();
 
     let request = wallet.start_full_scan().inspect_spks_for_all_keychains({
         let mut once = BTreeSet::<KeychainKind>::new();
         move |keychain, spk_i, _| {
-            match once.insert(keychain) {
-                true => print!("\nScanning keychain [{:?}]", keychain),
-                false => print!(" {:<3}", spk_i),
-            };
+            if once.insert(keychain) {
+                print!("\nScanning keychain [{:?}] ", keychain);
+            }
+            print!(" {:<3}", spk_i);
             std::io::stdout().flush().expect("must flush")
         }
     });
@@ -72,12 +76,9 @@ fn main() -> Result<(), anyhow::Error> {
         std::process::exit(0);
     }
 
-    let faucet_address = Address::from_str("mkHS9ne12qx9pS9VojpwU5xtRd4T7X7ZUt")?
-        .require_network(Network::Testnet)?;
-
     let mut tx_builder = wallet.build_tx();
     tx_builder
-        .add_recipient(faucet_address.script_pubkey(), SEND_AMOUNT)
+        .add_recipient(address.script_pubkey(), SEND_AMOUNT)
         .enable_rbf();
 
     let mut psbt = tx_builder.finish()?;