Introduce default_config function

.. this allows us the retrieve a `Config` prepopulated with default values in
bindings (where `Default::default()` isn't available), even if it
includes complex structures for which we can't set default values in the
UDL file.

Author: tnull

bindings/ldk_node.udl

@@ -1,19 +1,20 @@
 namespace ldk_node {
 	Mnemonic generate_entropy_mnemonic();
+	Config default_config();
 };
 
 dictionary Config {
-	string storage_dir_path = "/tmp/ldk_node/";
-	string? log_dir_path = null;
-	Network network = "Bitcoin";
-	sequence<SocketAddress>? listening_addresses = null;
-	u32 default_cltv_expiry_delta = 144;
-	u64 onchain_wallet_sync_interval_secs = 80;
-	u64 wallet_sync_interval_secs = 30;
-	u64 fee_rate_cache_update_interval_secs = 600;
-	sequence<PublicKey> trusted_peers_0conf = [];
-	u64 probing_liquidity_limit_multiplier = 3;
-	LogLevel log_level = "Debug";
+	string storage_dir_path;
+	string? log_dir_path;
+	Network network;
+	sequence<SocketAddress>? listening_addresses;
+	u32 default_cltv_expiry_delta;
+	u64 onchain_wallet_sync_interval_secs;
+	u64 wallet_sync_interval_secs;
+	u64 fee_rate_cache_update_interval_secs;
+	sequence<PublicKey> trusted_peers_0conf;
+	u64 probing_liquidity_limit_multiplier;
+	LogLevel log_level;
 };
 
 interface Builder {

src/lib.rs

@@ -278,6 +278,11 @@ impl Default for Config {
 	}
 }
 
+/// Returns a [`Config`] object with default values.
+pub fn default_config() -> Config {
+	Config::default()
+}
+
 /// The main interface object of LDK Node, wrapping the necessary LDK and BDK functionalities.
 ///
 /// Needs to be initialized and instantiated through [`Builder::build`].