Groups:

groups of users
have no special permissions
should not be discoverable in the catalog
should not be viewable in the "manage groups" view unless you have rights to manage that group
can be granted permission to edit works and collections
can have profiles (? not sure yet)
are manually created (in R1) but in the future releases will need to enable external systems for group membership.
can be created by any user in the system who has the rights to create groups

Wireframes:

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