Function ensure_subscription_routes 

pub fn ensure_subscription_routes(
    ids: &[InstrumentId],
    client_id: Option<&ClientId>,
    cache: &Cache,
) -> Result<()>

Checks identifier-list routing for instrument metadata, books, status, close, and option greeks.

External data clients handle these lists themselves.

Errors

Returns an error if the client is not external and the list contains multiple IDs with a synthetic member.