Building upon research for Default Target URI mapping, we want to drive this initiative further and open Site definitions to light development.

With YAML sites in mind, it is foreseen that we will configure all domains (for all instances in a project) in the same single site definition
—effectively having extra domains configured, even if a given instance is not bound to that domain.

One side-goal to this is to remove the need for per-instance JCR configuration regarding site/multisite setup.