This would allow wallet operations like funding transactions with smart contract-based inputs such as LN, or any input the Core wallet doesn't know how to sign for.

https://github.com/bitcoin/bitcoin/pull/17211#issuecomment-933674310
}
        if (options.exists("change_type")) {
            if (options.exists("changeAddress") || options.exists("change_address")) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both change address and address type options");
            }
            if (std::optional<OutputType> parsed = ParseOutputType(options["change_type"].get_str())) {
                coinControl.m_change_type.emplace(parsed.value());
            } else {
                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Unknown change type '%s'", options["change_type"].get_str()));
            }
        }
        const UniValue include_watching_option = options.exists("include_watching") ? options["include_watching"] : options["includeWatching"];
        coinControl.fAllowWatchOnly = ParseIncludeWatchonly(include_watching_option, wallet);
        if (options.exists("lockUnspents") || options.exists("lock_unspents")) {
            lockUnspents = (options.exists("lock_unspents") ? options["lock_unspents"] : options["lockUnspents"]).get_bool();
        }
        if (options.exists("include_unsafe")) {
            coinControl.m_include_unsafe_inputs = options["include_unsafe"].get_bool();
        }
        if (options.exists("feeRate")) {
            if (options.exists("fee_rate")) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both fee_rate (" + CURRENCY_ATOM + "/vB) and feeRate (" + CURRENCY_UNIT + "/kvB)");
            }
            if (options.exists("conf_target")) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both conf_target and feeRate. Please provide either a confirmation target in blocks for automatic fee estimation, or an explicit fee rate.");
            }
            if (options.exists("estimate_mode")) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both estimate_mode and feeRate");
            }
            coinControl.m_feerate = CFeeRate(AmountFromValue(options["feeRate"]));