Closes #4491: Update docs to indicate support for nesting objects

docs/models/dcim/rackgroup.md

@@ -2,6 +2,6 @@
 
 Racks can be arranged into groups. As with sites, how you choose to designate rack groups will depend on the nature of your organization. For example, if each site represents a campus, each group might represent a building within a campus. If each site represents a building, each rack group might equate to a floor or room.
 
-Each rack group must be assigned to a parent site. Hierarchical recursion of rack groups is not currently supported.
+Each rack group must be assigned to a parent site, and rack groups may optionally be nested to achieve a multi-level hierarchy.
 
 The name and facility ID of each rack within a group must be unique. (Racks not assigned to the same rack group may have identical names and/or facility IDs.)

docs/models/tenancy/tenantgroup.md

@@ -1,3 +1,5 @@
 # Tenant Groups
 
 Tenants can be organized by custom groups. For instance, you might create one group called "Customers" and one called "Acquisitions." The assignment of tenants to groups is optional.
+
+Tenant groups may be nested to achieve a multi-level hierarchy. For example, you might have a group called "Customers" containing subgroups of individual tenants grouped by product or account team.