No mention about _update permission available

[Thaina]

When I try to access $DB/_design/$doc/_update/$func without permission it then throw this error

{
    "error": "forbidden",
    "reason": "one of _update, _design, _writer is required for this request"
}

Which I has not see in any document that we could set permission to _update and let user can use only _update function but cannot write document directly

It also the same with _list too

Documenting about these features would encourage us to use more feature available in cloudant that could be secure with native system