Decode utf8 in opreturn and convert to hex

src/wallet/rpcwallet.cpp

@@ -5157,9 +5157,14 @@ UniValue z_sendmany(const UniValue& params, bool fHelp, const CPubKey& mypk)
     if(params.size() == 5) {
         opretValue = params[4].get_str();
 
+        // Support a prefix "utf8:" which allows giving utf8 text instead of hex
         if(opretValue.get_str().substr(0,5) == "utf8:") {
-            // TODO: 1) remove the first 5 chars
-            //       2) convert remaining text to hex and store in opretValue
+            auto str = opretValue.get_str().substr(5);
+            if (utf8::is_valid(str)) {
+                opretValue = HexStr(str);
+            } else {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid utf8 in opreturn");
+            }
         }
     }