add achievement management

app/models/wow_achievement_criterium.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class WowAchievementCriterium < ApplicationRecord
+  extend Mobility
+  translates :description, :operator_name
+
+  has_many :wow_achievements, dependent: :destroy
+  has_many :child_criteria,
+           class_name: 'WowAchievementCriterium',
+           foreign_key: 'parent_criterium_id',
+           dependent: :destroy,
+           inverse_of: :parent_criterium
+  belongs_to :parent_criterium, class_name: 'WowAchievementCriterium', optional: true
+  has_many :completed_wow_achievement_criteria, dependent: :destroy
+  has_many :wow_characters, through: :completed_wow_achievement_criteria
+
+  validates :criterium_id, presence: true, uniqueness: true
+end