"1" implies sampled and is a request to override collection-tier sampling policy.
64-bit parent span ID lower-hex encoded into 16 characters (absent on root span)
"1" means report this span to the tracing system, "0" means do not. (absent means defer the decision to the receiver of this header).
64-bit span ID lower-hex encoded into 16 characters (required)
128 or 64-bit trace ID lower-hex encoded into 32 or 16 characters (required)