Document what types of things SUSHI validates (and does not)

A user asked what does SUSHI validate when it runs, especially for instances against their profiles or base resources. I realized we don't have documentation on that.
It would be a nice addition to the SUSHI doc to have a table or list of what SUSHI does and does not validate about instances when it runs, e.g., path existence -- yes, cardinality - yes, slice matching - no, code in required value set - no, etc.