While some protocols require value attached to OP_RETURN outputs, this otherwise seems like a mistake.

Setting the value to 0 should really be done by the wallet/script creating the transaction (like createrawtransaction does for `data` outputs). However, as an additional check, similar to the high-fee check, sendrawtransaction could also check for non-zero value OP_RETURN outputs.

This should be configurable by a new RPC argument.

See also https://transactionfee.info/charts/output-opreturn-amount/

#### Useful skills:

* Bitcoin Core RPC code
* Transaction output types
* Bitcoin Core functional tests

#### Want to work on this issue?

For guidance on contributing, please read [CONTRIBUTING.md](https://github.com/bitcoin/bitcoin/blob/master/CONTRIBUTING.md) before opening your pull request.

o.pushKV("vout", (uint64_t)prevout.n);
                const CTransaction* spendingTx = mempool.GetConflictTx(prevout);
                if (spendingTx != nullptr) {
                    o.pushKV("spendingtxid", spendingTx->GetHash().ToString());
                }
                result.push_back(o);
            }
            return result;
        },
    };
}
UniValue MempoolInfoToJSON(const CTxMemPool& pool)
{
    
    LOCK(pool.cs);
    UniValue ret(UniValue::VOBJ);
    ret.pushKV("loaded", pool.GetLoadTried());
    ret.pushKV("size", (int64_t)pool.size());
    ret.pushKV("bytes", (int64_t)pool.GetTotalTxSize());
    ret.pushKV("usage", (int64_t)pool.DynamicMemoryUsage());
    ret.pushKV("total_fee", ValueFromAmount(pool.GetTotalFee()));
    ret.pushKV("maxmempool", pool.m_max_size_bytes);
    ret.pushKV("mempoolminfee", ValueFromAmount(std::max(pool.GetMinFee(), pool.m_min_relay_feerate).GetFeePerK()));
    ret.pushKV("minrelaytxfee", ValueFromAmount(pool.m_min_relay_feerate.GetFeePerK()));
    ret.pushKV("incrementalrelayfee", ValueFromAmount(pool.m_incremental_relay_feerate.GetFeePerK()));
    ret.pushKV("unbroadcastcount", uint64_t{pool.GetUnbroadcastTxs().size()});
    ret.pushKV("fullrbf", pool.m_full_rbf);
    return ret;
}
static RPCHelpMan getmempoolinfo()