Add changelog

CHANGELOG.md

@@ -4,6 +4,18 @@ Canonical reference for changes, improvements, and bugfixes for Boundary.
 
 ## Next
 
+### New and Improved
+
+* oidc: The new Managed Groups feature allows groups of accounts to be created
+  based on an authenticating user's JWT or User Info data. This data uses the
+  same filtering syntax found elsewhere in Boundary to provide a rich way to
+  specify the criteria for group membership. Once defined, authenticated users
+  are added to or removed from these groups as appropriateds each time they
+  authenticate. These groups are treated like other role principals and can be
+  added to roles to provide grants to users.
+* dev: Predictable IDs in `boundary dev` mode now extend to the accounts created
+  in the default `password` and `oidc` auth methods.
+
 ## 0.2.3 (2021/05/21)
 
 ### Deprecations/Changes