Expose Derive Child Api

Author: dhruv-1001

src/bdk.udl

@@ -3,6 +3,8 @@ namespace bdk {
   ExtendedKeyInfo generate_extended_key(Network network, WordCount word_count, string? password);
   [Throws=BdkError]
   ExtendedKeyInfo restore_extended_key(Network network, string mnemonic, string? password);
+  [Throws=BdkError]
+  ChildKeyPair derive_child_key_pair(string str_xprv, string str_path);
 };
 
 [Error]
@@ -173,6 +175,11 @@ dictionary ExtendedKeyInfo {
   string fingerprint;
 };
 
+dictionary ChildKeyPair {
+  string xprv;
+  string xpub;
+};
+
 enum WordCount {
   "Words12",
   "Words15",

src/lib.rs

@@ -322,8 +322,8 @@ fn restore_extended_key(
 }
 
 fn derive_child_key_pair(
-    str_path: String,
-    str_xprv: String
+    str_xprv: String,
+    str_path: String
 ) -> Result<ChildKeyPair, Error> {
     let secp = Secp256k1::new();
     let xprv = ExtendedPrivKey::from_str(&str_xprv)?;