Add GetNewChangeDestination for getting new change Destinations

Adds a GetNewChangeDestination that has the same objective as GetNewDestination

Author: achow101

src/wallet/rpcwallet.cpp

@@ -226,23 +226,18 @@ static UniValue getrawchangeaddress(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_WALLET_ERROR, "Error: This wallet has no available keys");
     }
 
-    if (!pwallet->IsLocked()) {
-        pwallet->TopUpKeyPool();
-    }
-
     OutputType output_type = pwallet->m_default_change_type != OutputType::CHANGE_AUTO ? pwallet->m_default_change_type : pwallet->m_default_address_type;
     if (!request.params[0].isNull()) {
         if (!ParseOutputType(request.params[0].get_str(), output_type)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Unknown address type '%s'", request.params[0].get_str()));
         }
     }
 
-    ReserveDestination reservedest(pwallet);
     CTxDestination dest;
-    if (!reservedest.GetReservedDestination(output_type, dest, true))
-        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, "Error: Keypool ran out, please call keypoolrefill first");
-
-    reservedest.KeepDestination();
+    std::string error;
+    if (!pwallet->GetNewChangeDestination(output_type, dest, error)) {
+        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, error);
+    }
     return EncodeDestination(dest);
 }
 

src/wallet/wallet.cpp

@@ -3531,6 +3531,23 @@ bool CWallet::GetNewDestination(const OutputType type, const std::string label,
     return true;
 }
 
+bool CWallet::GetNewChangeDestination(const OutputType type, CTxDestination& dest, std::string& error)
+{
+    error.clear();
+    if (!IsLocked()) {
+        TopUpKeyPool();
+    }
+
+    ReserveDestination reservedest(this);
+    if (!reservedest.GetReservedDestination(type, dest, true)) {
+        error = "Error: Keypool ran out, please call keypoolrefill first";
+        return false;
+    }
+
+    reservedest.KeepDestination();
+    return true;
+}
+
 static int64_t GetOldestKeyTimeInPool(const std::set<int64_t>& setKeyPool, WalletBatch& batch) {
     if (setKeyPool.empty()) {
         return GetTime();

src/wallet/wallet.h

@@ -1128,6 +1128,7 @@ class CWallet final : public CCryptoKeyStore, private interfaces::Chain::Notific
     std::set<CTxDestination> GetLabelAddresses(const std::string& label) const;
 
     bool GetNewDestination(const OutputType type, const std::string label, CTxDestination& dest, std::string& error);
+    bool GetNewChangeDestination(const OutputType type, CTxDestination& dest, std::string& error);
 
     isminetype IsMine(const CTxIn& txin) const;
     /**