Propagator W3C: async and sync Ring middleware implementation

[gabrielnau]

• check semconv
• https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/docs/semantic-conventions.md
• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md
• https://github.com/alvinfrancis/opentracing-clj/blob/master/src/clj/opentracing_clj/ring.clj