Function parse_ws_funding_rate_update 

pub fn parse_ws_funding_rate_update(
    stats: &LighterMarketStats,
    instrument: &InstrumentAny,
    timestamp_ms: u64,
    ts_init: UnixNanos,
) -> Result<FundingRateUpdate>

Parses a Lighter perpetual market-stat update into a funding-rate update.

Lighter exposes current_funding_rate as the estimate for the upcoming payment. The funding_rate field is the last completed payment, so it is not used for the streaming Nautilus update.

Errors

Returns an error if the funding rate, event timestamp, or funding timestamp cannot be converted.