pub const TRACEPARENT: &str = "traceparent";Expand description
The RESERVED envelope header carrying W3C Trace Context’s traceparent.
The header name is specified here because an unwritten convention becomes multiple incompatible conventions across SDKs. The key is lowercase because W3C Trace Context defines these as HTTP header field names, which are case-insensitive on the wire and canonically lowercase; the envelope’s header map is NOT case-insensitive, so the spec has to pick one spelling and this is it.