message: docs: adds information about the Envoy tracer from Instana
diff: @@ -12,14 +12,18 @@ sources of latency. Envoy supports three features related to system wide tracing
  * **Request ID generation**: Envoy will generate UUIDs when needed and populate the
  :ref:`config_http_conn_man_headers_x-request-id` HTTP header. Applications can forward the
  x-request-id header for unified logging as well as tracing.
  -* **External trace service integration**: Envoy supports pluggable external trace visualization
  - providers. Currently Envoy supports `LightStep <https://lightstep.com/>`_, `Zipkin <https://zipkin.io/>`_
  - or any Zipkin compatible backends (e.g. `Jaeger <https://github.com/jaegertracing/>`_), and
  - `Datadog <https://datadoghq.com>`_.
  - However, support for other tracing providers would not be difficult to add.
  * **Client trace ID joining**: The :ref:`config_http_conn_man_headers_x-client-trace-id` header can
  be used to join untrusted request IDs to the trusted internal
  :ref:`config_http_conn_man_headers_x-request-id`.
  +* **External trace service integration**: Envoy supports pluggable external trace visualization
  + providers, that are divided into two subgroups:
  +
  + - External tracers which are part of the Envoy code base, like `LightStep <https://lightstep.com/>`_,
  + `Zipkin <https://zipkin.io/>`_ or any Zipkin compatible backends (e.g. `Jaeger <https://github.com/jaegertracing/>`_), and
  + `Datadog <https://datadoghq.com>`_.
  + - External tracers which come as a third party plugin, like `Instana <https://www.instana.com/blog/monitoring-envoy-proxy-microservices/>`_.
  +
  +Support for other tracing providers would not be difficult to add.
  How to initiate a trace
  -----------------------
  