Merge branch 'issue_subscription' into 'master'

Subscription to issue/mr

Fixes #1911 and #1909

![joxi_screenshot_1426601822159](https://dev.gitlab.org/gitlab/gitlabhq/uploads/53021bc5783271322ab2dfba7598eaa3/joxi_screenshot_1426601822159.png)

![joxi_screenshot_1426601836423](https://dev.gitlab.org/gitlab/gitlabhq/uploads/244ff360fbd6f30980f8dad699400814/joxi_screenshot_1426601836423.png)

See merge request !1702

1 files changed, 16 insertions, 0 deletions

diff --git a/db/migrate/20150313012111_create_subscriptions_table.rb b/db/migrate/20150313012111_create_subscriptions_table.rb
new file mode 100644
index 00000000000..a1d4d9dedc5
--- /dev/null
+++ b/db/migrate/20150313012111_create_subscriptions_table.rb
@@ -0,0 +1,16 @@
+class CreateSubscriptionsTable < ActiveRecord::Migration
+  def change
+    create_table :subscriptions do |t|
+      t.integer :user_id
+      t.references :subscribable, polymorphic: true
+      t.boolean :subscribed
+      
+      t.timestamps
+    end
+
+    add_index :subscriptions, 
+              [:subscribable_id, :subscribable_type, :user_id],
+              unique: true,
+              name: 'subscriptions_user_id_and_ref_fields'
+  end
+end