Organize Serializer concerns into concerns/

lib/active_model/serializer/concerns/configuration.rb

@@ -0,0 +1,37 @@
+module ActiveModel
+  class Serializer
+    module Configuration
+      include ActiveSupport::Configurable
+      extend ActiveSupport::Concern
+
+      # Configuration options may also be set in
+      # Serializers and Adapters
+      included do |base|
+        config = base.config
+        config.collection_serializer = ActiveModel::Serializer::CollectionSerializer
+        config.serializer_lookup_enabled = true
+
+        def config.array_serializer=(collection_serializer)
+          self.collection_serializer = collection_serializer
+        end
+
+        def config.array_serializer
+          collection_serializer
+        end
+
+        config.default_includes = '*'
+        config.adapter = :attributes
+        config.key_transform = nil
+        config.jsonapi_resource_type = :plural
+        config.jsonapi_namespace_separator = '-'.freeze
+        config.jsonapi_version = '1.0'
+        config.jsonapi_toplevel_meta = {}
+        # Make JSON API top-level jsonapi member opt-in
+        # ref: http://jsonapi.org/format/#document-top-level
+        config.jsonapi_include_toplevel_object = false
+
+        config.schema_path = 'test/support/schemas'
+      end
+    end
+  end
+end