define sign_txs() and submit_txs() in monero_wallet.h

src/wallet/monero_wallet.h

@@ -1103,6 +1103,26 @@ namespace monero {
       throw runtime_error("parse_tx_set() not supported");
     }
 
+    /**
+     * Sign unsigned transactions from a watch-only wallet.
+     *
+     * @param unsigned_tx_hex is unsigned transaction hex from when the transactions were created
+     * @return the signed transaction hex
+     */
+    virtual string sign_txs(const string& unsigned_tx_hex) {
+      throw runtime_error("parse_tx_set() not supported");
+    }
+
+    /**
+     * Submit signed transactions from a watch-only wallet.
+     *
+     * @param signed_tx_hex is signed transaction hex from signTxs()
+     * @return the resulting transaction hashes
+     */
+    vector<string> submit_txs(const string& signed_tx_hex) {
+      throw runtime_error("parse_tx_set() not supported");
+    }
+
     /**
      * Sign a message.
      *