Documentation Improvement - Service Mesh and Envoy Filters

The service mesh and envoy capabilities being added to Consul are of huge interest but right now all examples are relatively simple and are hard to apply to the "real world" outside of a few fake service demos.

It would be great to see some examples on how the Mesh features can plug in, or extend, the use of filters. Common examples are Zookeeper, Kafka, Postgres, etc. I would venture that anyone considering service mesh has, at a minimum, a messaging system and a db of sorts.

Another example would be how to "migrate" to service mesh. An example here is that a lot of us have these legacy systems AND new microservice systems without Mesh already enabled. Doing a "big bang" isn't really viable or practical so having some best practices around how to slowly add on Consul features and work Mesh in to existing deployments would also be very helpful and give users a way of thinking about their current->future migrations.

Thanks for your consideration :)

Ian