Function edge_key_from 

pub fn edge_key_from(caller: &str) -> Option<String>

I2 (#1971): the edge keys’ names, for the driver (bynk dev, bynk deploy), which sees the compiler only through this crate. I2 (#1971): the secret the callee holds for calls from caller (BYNK_CALL_FROM_SHOP__ORDERS). The callee picks it by the request’s CALLER_HEADER, so an undeclared caller finds no key and is refused.