LB ACLs imported/converted into runtime representation in SL Gateway

[altsang]

As a LB user, I have the ability to define ACLs on the model level to a fine level of granularity. Models are automatically scaffolded into a REST API. Because I've defined this once already at the model level, I don't want to have to re-do this again at the gateway level.

• need to be able to convert

[raymondfeng]

We'll need to allow the ACL specs for models to be published to a metadata registry so that the gateway can have access to them. It could be possibly an extension to api spec publishing.