values smaller than 0.001 sat/B can't be represented by CFeeRate, but they are not rejected.

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.0009

error code: -6
error message:
Fee rate (0.000 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)
```

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.000000000009

error code: -3
error message:
Invalid amount

{
    return RPCHelpMan{"setlabel",
                "\nSets the label associated with the given address.\n",
                {
                    {"address", RPCArg::Type::STR, RPCArg::Optional::NO, "The bitcoin address to be associated with a label."},
                    {"label", RPCArg::Type::STR, RPCArg::Optional::NO, "The label to assign to the address."},
                },
                RPCResult{RPCResult::Type::NONE, "", ""},
                RPCExamples{
                    HelpExampleCli("setlabel", "\"" + EXAMPLE_ADDRESS[0] + "\" \"tabby\"")
            + HelpExampleRpc("setlabel", "\"" + EXAMPLE_ADDRESS[0] + "\", \"tabby\"")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    std::shared_ptr<CWallet> const pwallet = GetWalletForJSONRPCRequest(request);
    if (!pwallet) return NullUniValue;
    LOCK(pwallet->cs_wallet);
    CTxDestination dest = DecodeDestination(request.params[0].get_str());
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address");
    }
    std::string label = LabelFromValue(request.params[1]);
    if (pwallet->IsMine(dest)) {
        pwallet->SetAddressBook(dest, label, "receive");
    } else {
        pwallet->SetAddressBook(dest, label, "send");
    }