dd-trace-rb: Improper parsing of W3C baggage headers may lead to DoS

dd-trace-rb is Datadog's client library for Ruby. Prior to 2.32.0, W3C baggage extraction does not enforce DD_TRACE_BAGGAGE_MAX_ITEMS, which defaults to 64, or DD_TRACE_BAGGAGE_MAX_BYTES, which defaults to 8192, although those limits apply during baggage injection. A remote unauthenticated attacker can send a baggage HTTP header containing many comma-separated key-value pairs or a single very large value. The extraction path allocates entries while parsing the attacker-controlled header on every request, causing unbounded CPU and memory consumption in an HTTP service where the baggage propagation style is enabled, which is the default for most affected tracers. This can cause denial of service. This issue is fixed in version 2.32.0.