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{"getnewaddress",
                "\nReturns a new Bitcoin address for receiving payments.\n"
                "If 'label' is specified, it is added to the address book \n"
                "so payments received with the address will be associated with 'label'.\n",
                {
                    {"label", RPCArg::Type::STR, RPCArg::Default{""}, "The label name for the address to be linked to. It can also be set to the empty string \"\" to represent the default label. The label does not need to exist, it will be created if there is no label by the given name."},
                    {"address_type", RPCArg::Type::STR, RPCArg::DefaultHint{"set by -addresstype"}, "The address type to use. Options are \"legacy\", \"p2sh-segwit\", and \"bech32\"."},
                },
                RPCResult{
                    RPCResult::Type::STR, "address", "The new bitcoin address"
                },
                RPCExamples{
                    HelpExampleCli("getnewaddress", "")
            + HelpExampleRpc("getnewaddress", "")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    std::shared_ptr<CWallet> const pwallet = GetWalletForJSONRPCRequest(request);
    if (!pwallet) return NullUniValue;
    LOCK(pwallet->cs_wallet);
    if (!pwallet->CanGetAddresses()) {