add ruby updated info for email service

src/emailservice/README.md

@@ -21,3 +21,40 @@ You may run this service locally with `bundle exec ruby email_server.rb`.
 ## Building docker image
 
 From `src/emailservice`, run `docker build .`
+
+## OpenTelemetry features
+
+### Emoji Legend
+
+- Completed: :100:
+- Not Present (Yet): :construction:
+
+### Traces
+
+- :100: [Instrumentation
+  Libraries](https://opentelemetry.io/docs/concepts/instrumenting-library/)
+- :100: [Manual Span
+  Creation](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/glossary.md#manual-instrumentation)
+- :100: [Span Data
+  Enrichment](https://opentelemetry.io/docs/instrumentation/net/manual/#add-tags-to-an-activity)
+- :100: Interprocess Context Propagation
+- :construction: [Intra-service Context
+  Propagation](https://opentelemetry.io/docs/instrumentation/java/manual/#context-propagation)
+- :construction: [Trace
+  Links](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/overview.md#links-between-spans)
+- :construction:
+  [Baggage](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/baggage/api.md#overview)
+
+### Metrics
+
+- :construction: [Instrumentation
+  Libraries](https://opentelemetry.io/docs/concepts/instrumenting-library/)
+- :construction: [Manual Metric
+  Creation](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/glossary.md#manual-instrumentation)
+- :construction: [Collector Agent Metric
+  Transformation](https://opentelemetry.io/docs/collector/deployment/#agent)
+- :construction: [Push
+  Metrics](https://opentelemetry.io/docs/reference/specification/metrics/sdk/#push-metric-exporter)
+- :construction: [SLO Metrics](https://github.com/openslo/openslo#slo)
+- :construction: [Multiple Manual Metric
+  Instruments](https://opentelemetry.io/docs/reference/specification/metrics/api/#synchronous-and-asynchronous-instruments)