Function has_te_trailers 

pub fn has_te_trailers(headers: &Headers) -> bool

Validate that the request carries te: trailers. The gRPC HTTP/2 spec requires this so HTTP/2 intermediaries don’t strip response trailers.

Returns true if any value of the te header equals trailers (case-insensitive). te is a list-valued header, so multiple comma-separated values or multiple header lines are both accepted.