Allow creating partially signed bitcoin transactions

bindings/bdk-kotlin/demo/src/main/kotlin/Main.kt

@@ -2,24 +2,28 @@ import uniffi.bdk.*
 
 class LogProgress: BdkProgress {
     override fun update(progress: Float, message: String? ) {
-        println(progress);
-        println(message);
+        println("progress: $progress, message: $message")
     }
 }
 
 fun main(args: Array<String>) {
+    println("Configuring an in-memory wallet on electrum..")
     val descriptor =
         "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/0/*)";
+    val amount = 10000uL;
+    val recipient = "tb1ql7w62elx9ucw4pj5lgw4l028hmuw80sndtntxt";
     val db = DatabaseConfig.Memory("")
     val client = BlockchainConfig.Electrum(ElectrumConfig("ssl://electrum.blockstream.info:60002", null, 5u, null, 100u))
     val wallet = OnlineWallet(descriptor, Network.TESTNET, db, client)
     val address = wallet.getNewAddress()
-    println("Please send satoshis to wallet address: $address")
+    println("Please send $amount satoshis to address: $address")
     readLine()
     println("Syncing...")
     wallet.sync(LogProgress(), null)
     val balance = wallet.getBalance()
     println("New wallet balance: $balance")
+    println("Refunding $amount satoshis to $recipient")
+    val psbt = PartiallySignedBitcoinTransaction(wallet, recipient, amount)
     println("Press any key to exit")
     readLine()
 }