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

: m_left{left}, m_right{right} {}
    std::string m_left;
    const std::string m_right;
};
/**
 * Keeps track of RPCArgs by transforming them into sections for the purpose
 * of serializing everything to a single string
 */
struct Sections {
    std::vector<Section> m_sections;
    size_t m_max_pad{0};
    void PushSection(const Section& s)
    {
        m_max_pad = std::max(m_max_pad, s.m_left.size());
        m_sections.push_back(s);
    }
    /**
     * Recursive helper to translate an RPCArg into sections
     */
    void Push(const RPCArg& arg, const size_t current_indent = 5, const OuterType outer_type = OuterType::NONE)