add achievement management

app/models/wow_achievement_category.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class WowAchievementCategory < ApplicationRecord
+  extend Mobility
+  translates :name
+
+  has_many :wow_achievements, dependent: :destroy
+
+  validates :name, presence: true
+  validates :category_id, presence: true, uniqueness: true
+end