A warning should be provided if a table is added to a Target/Source and the schema doesn't match the schema recorded in the Group. Any and all Schemas found in the group should be indicated.
FETCH fetches all schema owners (this seems like a good thing. It might be good for each schema to be put in a separate group, but we should NOT, at this time, FILTER on the schema registered in the source unless we also indicate that there are tables in other schemas.