Specify that mesh gateways require Envoy (#6506)
Specify that mesh gateways require Envoy (#6506)

* Specify that mesh gateways must operate on L7

* Add feedback from Matt

* clarify gateway requirements

scalp42/consul,hashicorp/consul,hashicorp/consul,kingland/consul,hashicorp/consul,kingland/consul,scalp42/consul,kingland/consul,scalp42/consul,42wim/consul,scalp42/consul,kingland/consul,42wim/consul,kingland/consul,42wim/consul,42wim/consul,hashicorp/consul,42wim/consul,scalp42/consul