document different types of router deployments

[qrkourier]

public, private at least. These aren't ziti terms but rather popular jargon for distinguishing between routers with a transport link lister (public) or not (private). The only difference is whether the router's address is presumed reachable by all other routers.

There's no reason all routers can't be public routers (listening for mesh transport links). The reason to turn off link listeners on some routers is to limit connection error messages in logs because all routers continually try to connect to all link listeners to form a full mesh of fabric links.

Mention fabric or non-traversal routers? Fabric only means no edge listener. A fabric-only router can be public or private. The other flag that influences data plane topology is non-traversal. Document these in the context of "how to accomplish X" as a stepwise guide.

do this after: https://github.com/openziti/ziti/issues/2003