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.

{ "disconnectnode", 1, "nodeid" },
    { "upgradewallet", 0, "version" },
    
    { "echojson", 0, "arg0" },
    { "echojson", 1, "arg1" },
    { "echojson", 2, "arg2" },
    { "echojson", 3, "arg3" },
    { "echojson", 4, "arg4" },
    { "echojson", 5, "arg5" },
    { "echojson", 6, "arg6" },
    { "echojson", 7, "arg7" },
    { "echojson", 8, "arg8" },
    { "echojson", 9, "arg9" },
    { "rescanblockchain", 0, "start_height"},
    { "rescanblockchain", 1, "stop_height"},
    { "createwallet", 1, "disable_private_keys"},
    { "createwallet", 2, "blank"},
    { "createwallet", 4, "avoid_reuse"},
    { "createwallet", 5, "descriptors"},
    { "createwallet", 6, "load_on_startup"},
    { "createwallet", 7, "external_signer"},
    { "restorewallet", 2, "load_on_startup"},
    { "loadwallet", 1, "load_on_startup"},
    { "unloadwallet", 1, "load_on_startup"},
    { "getnodeaddresses", 0, "count"},
    { "addpeeraddress", 1, "port"},
    { "addpeeraddress", 2, "tried"},
    { "stop", 0, "wait" },
};
class CRPCConvertTable