Added newsletter model and UserSegments class

app/models/newsletter.rb

@@ -0,0 +1,23 @@
+class Newsletter < ActiveRecord::Base
+  enum segment_recipient: { all_users: 1,
+                            proposal_authors: 2,
+                            investment_authors: 3,
+                            feasible_and_undecided_investment_authors: 4,
+                            selected_investment_authors: 5,
+                            winner_investment_authors: 6 }
+
+  validates :subject, presence: true
+  validates :segment_recipient, presence: true
+  validates :from, presence: true
+  validates :body, presence: true
+
+  validates_format_of :from, :with => /@/
+
+  def list_of_recipients
+    UserSegments.send(segment_recipient)
+  end
+
+  def draft?
+    sent_at.nil?
+  end
+end