v0.5.0 for API, SDK and OTLP Exporter

Major change in this release is we now match the spec for start_span, meaning it no longer sets the started Span to the current Span in the Context. To start a Span and set it to the current Span use with_span or pass the return value of start_span to set_current_span.

Some PR links are missing because they were made before the repos were combined.

API

• fix add_event macro to call otel_span:add_event/3
• move propagators to the api
• set is_recording to false when span is ended
• OTEL_RESOURCE_(LABELS -> ATTRIBUTES)
• remove Tracer argument when not used and add span ops to otel_span
• add Elixir modules for baggage and context
• remove context modification in start and end_span
• Add support for tuple attr values
• Add support for atoms in attributes

SDK

• update sampler to take a context and update some names to match spec
• set and test the default sampler
• add get_description to sampler and support for updating tracestate in sampler
• update samplers to latest spec: parent_based & trace_id_ratio_based
• Remove child span count - deprecated

Exporter

• update protos
• HTTP 1.1 Protobuf export support added