Currently, we use `assert` in RPC code to document logic and code assumptions. However, it seems a bit extreme to abort all of Bitcoin Core on an assert failure in one of the RPC threads. I suggest to replace all checks with a macro `THROW_LOGIC_ERROR_IF_ASSERT_FAILS(condition)` that does what it says. That logic error will then be returned to the rpc caller and will include instructions to report the error to our issue tracker.

Any objections or naming suggestions for that macro?
{
            RPCHelpMan{"signmessagewithprivkey",
                "\nSign a message with the private key of an address\n",
                {
                    {"privkey", RPCArg::Type::STR, RPCArg::Optional::NO, "The private key to sign the message with."},
                    {"message", RPCArg::Type::STR, RPCArg::Optional::NO, "The message to create a signature of."},
                },
                RPCResult{
            "\"signature\"          (string) The signature of the message encoded in base 64\n"
                },
                RPCExamples{
            "\nCreate the signature\n"
            + HelpExampleCli("signmessagewithprivkey", "\"privkey\" \"my message\"") +
            "\nVerify the signature\n"
            + HelpExampleCli("verifymessage", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" \"signature\" \"my message\"") +
            "\nAs a JSON-RPC call\n"
            + HelpExampleRpc("signmessagewithprivkey", "\"privkey\", \"my message\"")
                },
            }.Check(request);
    std::string strPrivkey = request.params[0].get_str();
    std::string strMessage = request.params[1].get_str();
    CKey key = DecodeSecret(strPrivkey);
    if (!key.IsValid()) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid private key");
    }
    CHashWriter ss(SER_GETHASH, 0);
    ss << strMessageMagic;