Selective discovery

[christian-posta]

trafficstars

Right now discovery finds all workloads and traffic targets in a mesh when a cluster is registered. We should be able to restrict which workloads/traffic targets are discovered by using selectors and labels to configure discovery to only find those services

[liorokman]

This issue might be a duplicate of #804 .

[EItanya]

This issue might be a duplicate of #804 .

That is a good point, but I do think this is slightly different. Restrictive federation limits the services which are exposed to other clusters. This issue is determining the services/workloads which our system discovers in the first place