Extract serializable as module again

app/models/queries/filters/serializable.rb

@@ -28,21 +28,22 @@
 # See doc/COPYRIGHT.rdoc for more details.
 #++
 
-require_relative 'base'
-
 module Queries
   module Filters
-    class Serializable < Base
+    module Serializable
       include ActiveModel::Serialization
+      extend ActiveSupport::Concern
 
-      # (de-)serialization
-      def self.from_hash(filter_hash)
-        filter_hash.keys.map do |field|
-          begin
-            create!(name, filter_hash[field])
-          rescue ::Queries::Filters::InvalidError
-            Rails.logger.error "Failed to constantize field filter #{field} from hash."
-            ::Queries::NotExistingFilter.create!(field)
+      class_methods do
+        # (de-)serialization
+        def from_hash(filter_hash)
+          filter_hash.keys.map do |field|
+            begin
+              create!(name, filter_hash[field])
+            rescue ::Queries::Filters::InvalidError
+              Rails.logger.error "Failed to constantize field filter #{field} from hash."
+              ::Queries::NotExistingFilter.create!(field)
+            end
           end
         end
       end

app/models/queries/filters/shared/custom_fields/base.rb

@@ -30,7 +30,9 @@
 
 module Queries::Filters::Shared
   module CustomFields
-    class Base < Queries::Filters::Serializable
+    class Base < Queries::Filters::Base
+      include Queries::Filters::Serializable
+
       attr_reader :custom_field
       attr_reader :custom_field_context
 

app/models/queries/work_packages/filter/work_package_filter.rb

@@ -28,7 +28,9 @@
 # See doc/COPYRIGHT.rdoc for more details.
 #++
 
-class Queries::WorkPackages::Filter::WorkPackageFilter < ::Queries::Filters::Serializable
+class Queries::WorkPackages::Filter::WorkPackageFilter < ::Queries::Filters::Base
+  include ::Queries::Filters::Serializable
+
   self.model = WorkPackage
 
   def human_name