Marks an Ash resource as a SCIM Group resource per RFC 7643 §4.2.

Add to your group resource:

defmodule MyApp.Accounts.Group do
  use Ash.Resource,
    domain: MyApp.Accounts,
    extensions: [AshScim.Group]

  scim do
    map :displayName, attribute: :name

    multivalued :members do
      map :value, attribute: :user_id
    end
  end

  # ... attributes, actions, relationships, etc.
end

See AshScim.Dsl.Map, AshScim.Dsl.Complex, and AshScim.Dsl.Multivalued for the per-entity options.