Allow for a pluggable minter service (#1295)

lib/active_fedora/persistence.rb

@@ -2,6 +2,13 @@ module ActiveFedora
   # = Active Fedora Persistence
   module Persistence
     extend ActiveSupport::Concern
+    extend ActiveSupport::Autoload
+    autoload :NullIdentifierService
+
+    included do
+      class_attribute :identifier_service_class
+      self.identifier_service_class = NullIdentifierService
+    end
 
     def new_record?
       return true if @ldp_source.subject.nil?
@@ -209,7 +216,13 @@ def execute_sparql_update
       end
 
       # Override to tie in an ID minting service
-      def assign_id; end
+      def assign_id
+        identifier_service.mint
+      end
+
+      def identifier_service
+        @identifier_service ||= identifier_service_class.new
+      end
 
       # This is only used when creating a new record. If the object doesn't have an id
       # and assign_id can mint an id for the object, then assign it to the resource.

lib/active_fedora/persistence/null_identifier_service.rb

@@ -0,0 +1,11 @@
+module ActiveFedora
+  module Persistence
+    # An identifier service that doesn't mint IDs, so that the autocreated
+    # identifiers from Fedora will be used.
+    class NullIdentifierService
+      # Effectively a no-op
+      # @return [NilClass]
+      def mint; end
+    end
+  end
+end