feat(wallet): add lookahead as optional argument

Using the default argument here, so this should actually be
non-breaking. Compared to a builder this is ergonomic in the target
languages IMO

Author: rustaceanrob

bdk-ffi/src/tx_builder.rs

@@ -617,6 +617,7 @@ mod tests {
             Arc::new(Descriptor::new(internal_descriptor, Network::Signet).unwrap()),
             Network::Signet,
             Arc::new(Connection::new_in_memory().unwrap()),
+            None,
         )
         .unwrap();
         let client = EsploraClient::new("https://mutinynet.com/api/".to_string(), None);

bdk-ffi/src/wallet.rs

@@ -41,23 +41,23 @@ impl Wallet {
     /// Build a new Wallet.
     ///
     /// If you have previously created a wallet, use load instead.
-    #[uniffi::constructor]
+    #[uniffi::constructor(default(lookahead = None))]
     pub fn new(
         descriptor: Arc<Descriptor>,
         change_descriptor: Arc<Descriptor>,
         network: Network,
         connection: Arc<Connection>,
+        lookahead: Option<u32>,
     ) -> Result<Self, CreateWithPersistError> {
         let descriptor = descriptor.to_string_with_secret();
         let change_descriptor = change_descriptor.to_string_with_secret();
         let mut binding = connection.get_store();
         let db: &mut BdkConnection = binding.borrow_mut();
-
-        let wallet: PersistedWallet<BdkConnection> =
-            BdkWallet::create(descriptor, change_descriptor)
-                .network(network)
-                .create_wallet(db)?;
-
+        let mut params = BdkWallet::create(descriptor, change_descriptor).network(network);
+        if let Some(lookahead) = lookahead {
+            params = params.lookahead(lookahead);
+        }
+        let wallet: PersistedWallet<BdkConnection> = params.create_wallet(db)?;
         Ok(Wallet {
             inner_mutex: Mutex::new(wallet),
         })