♻️ Extract Hyrax::GroupBehavior

As of 2023-11-09, [Hyrax::Group in Hyku's main branch][1] inherits
from ApplicationRecord.  This means to share logic between the two
requires that we extract a module (as we cannot change inheritance).

This commit is that effort.

[1]: https://github.com/samvera/hyku/blob/dd0da8061c2ee0233e4f32f8ea7748eda2792ba3/app/models/hyrax/group.rb#L6

app/models/hyrax/group.rb

@@ -1,49 +1,20 @@
 # frozen_string_literal: true
+
 module Hyrax
+  ##
+  # A Plain Old Ruby Object (PORO) representing a named group.
+  #
+  # In Hyku, we replace the PORO with an Application Record.  But there is significant duplication
+  # of logic.
+  #
+  # @see Hyrax::GroupBehavior
   class Group
-    DEFAULT_NAME_PREFIX = 'group/'
-
-    def self.name_prefix
-      DEFAULT_NAME_PREFIX
-    end
-
-    ##
-    # @return [Hyrax::Group]
-    def self.from_agent_key(key)
-      new(key.delete_prefix(name_prefix))
-    end
+    include Hyrax::GroupBehavior
 
     def initialize(name)
       @name = name
     end
 
     attr_reader :name
-
-    ##
-    # @return [Boolean]
-    def ==(other)
-      other.class == self.class && other.name == name
-    end
-
-    ##
-    # @return [String] a local identifier for this group; for use (e.g.) in ACL
-    #   data
-    def agent_key
-      self.class.name_prefix + name
-    end
-
-    def to_sipity_agent
-      sipity_agent || create_sipity_agent!
-    end
-
-    private
-
-    def sipity_agent
-      Sipity::Agent.find_by(proxy_for_id: name, proxy_for_type: self.class.name)
-    end
-
-    def create_sipity_agent!
-      Sipity::Agent.create!(proxy_for_id: name, proxy_for_type: self.class.name)
-    end
   end
 end

app/models/hyrax/group_behavior.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+module Hyrax
+  ##
+  # An {ActiveSupport::Concern} module that contains the {Hyrax::Group} logic.  It is extracted to a
+  # behavior because downstream Hyku has a Hyrax::Group that inherits from ApplicationRecord.  In
+  # other words it eschews the plain old Ruby object (PORO).  However, both Hyku and Hyrax's
+  # {Hyrax::Group} both have notable amounts of duplicated logic.
+  #
+  # @see Hyrax::Group
+  module GroupBehavior
+    extend ActiveSupport::Concern
+
+    DEFAULT_NAME_PREFIX = 'group/'
+
+    class_methods do
+      ##
+      # @return [String]
+      # @see DEFAULT_NAME_PREFIX
+      def name_prefix
+        DEFAULT_NAME_PREFIX
+      end
+
+      ##
+      # @return [Hyrax::Group]
+      def from_agent_key(key)
+        new(key.delete_prefix(name_prefix))
+      end
+    end
+
+    ##
+    # @return [Boolean]
+    def ==(other)
+      other.class == self.class && other.name == name
+    end
+
+    ##
+    # @return [String] a local identifier for this group; for use (e.g.) in ACL
+    #   data
+    def agent_key
+      self.class.name_prefix + name
+    end
+
+    def to_sipity_agent
+      sipity_agent || create_sipity_agent!
+    end
+
+    private
+
+    def sipity_agent
+      Sipity::Agent.find_by(proxy_for_id: name, proxy_for_type: self.class.name)
+    end
+
+    def create_sipity_agent!
+      Sipity::Agent.create!(proxy_for_id: name, proxy_for_type: self.class.name)
+    end
+  end
+end