v0.5.0

Added

• Derive Clone for B3Propagator, SamplingResult, and SpanBuilder
• Ability to configure the span id / trace id generator
• impl From<T> for common Key and Value types
• Add global tracer method
• Add Resource API
• Add Context API
• Add Correlations API
• Add HttpTextCompositePropagator for composing HttpTextPropagators
• Add GlobalPropagator for globally configuring a propagator
• Add TraceContextExt to provide methods for working with trace data in a context
• Expose EvictedQueue constructor

Changed

• Ensure that impls of Span are Send and Sync when used in global
• Changed Key and Value method signatures to remove Cow references
• Tracer's start now uses the implicit current context instead of an explicit span context.
  start_with_context may be used to specify a context if desired.
• with_span now accepts a span for naming consistency and managing the active state of a more
  complex span (likely produced by a builder), and the previous functionality that accepts a
  &str has been renamed to in_span, both of which now yield a context to the provided closure.
• Tracer's get_active_span now accepts a closure
• The Instrument trait has been renamed to FutureExt to avoid clashing with metric instruments,
  and instead accepts contexts via with_context.
• Span's get_context method has been renamed to span_context to avoid ambiguity.
• HttpTextPropagators inject the current context instead of an explicit span context. The context
  can be specified with inject_context.
• SpanData's context has been renamed to span_context

Fixed

• Update the probability sampler to match the spec
• Rename Traceparent header to traceparent

Removed

• TracerGenerics methods have been folded in to the Tracer trait so it is longer needed
• Tracer's mark_span_as_inactive has been removed
• Exporters no longer require an as_any method
• Span's mark_as_active, mark_as_inactive, and as_any have been removed