Add progress bar model

app/models/concerns/milestoneable.rb

@@ -5,5 +5,7 @@ module Milestoneable
     has_many :milestones, as: :milestoneable, dependent: :destroy
 
     scope :with_milestones, -> { joins(:milestones).distinct }
+
+    has_many :progress_bars, as: :progressable
   end
 end

app/models/progress_bar.rb

@@ -0,0 +1,28 @@
+class ProgressBar < ActiveRecord::Base
+  self.inheritance_column = nil
+  RANGE = 0..100
+
+  enum kind: %i[primary secondary]
+
+  belongs_to :progressable, polymorphic: true
+
+  translates :title, touch: true
+  include Globalizable
+
+  validates :progressable, presence: true
+  validates :kind, presence: true,
+            uniqueness: {
+              scope: [:progressable_type, :progressable_id],
+              conditions: -> { primary }
+            }
+  validates :percentage, presence: true, inclusion: RANGE, numericality: { only_integer: true }
+
+  before_validation :assign_progress_bar_to_translations
+  validates_translation :title, presence: true, unless: :primary?
+
+  private
+
+    def assign_progress_bar_to_translations
+      translations.each { |translation| translation.globalized_model = self }
+    end
+end

app/models/progress_bar/translation.rb

@@ -0,0 +1,3 @@
+class ProgressBar::Translation < Globalize::ActiveRecord::Translation
+  delegate :primary?, to: :globalized_model
+end