Add new permission for viewing announcements

Fixes CNVS-26824

Test plan:
 - Go to an account's permissions page
 - Ensure that a permission titled "View Announcements" shows up
 - Ensure that all course roles have it by default

Change-Id: Icfd19b4a218fcdadf43fd571a5362b76545cfabc
Reviewed-on: https://gerrit.instructure.com/71725
Reviewed-by: Steven Burnett <sburnett@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
Tested-by: Jenkins
QA-Review: Heath Hales <hhales@instructure.com>
Product-Review: Allison Weiss <allison@instructure.com>

app/controllers/role_overrides_controller.rb

@@ -269,6 +269,7 @@ class RoleOverridesController < ApplicationController
   #     read_forum                       -- [STADO] View discussions
   #     moderate_forum                   -- [sTADo] Moderate discussions (delete/edit others' posts, lock topics)
   #     post_to_forum                    -- [STADo] Post to discussions
+  #     read_announcements               -- [STADO] View announcements
   #     read_question_banks              -- [ TADo] View and link to question banks
   #     read_reports                     -- [ TAD ] View usage reports for the course
   #     read_roster                      -- [STADo] See the list of users

app/models/role_override.rb

@@ -148,6 +148,27 @@ class RoleOverride < ActiveRecord::Base
           'AccountAdmin'
         ]
       },
+      :read_announcements => {
+        :label => lambda { t('View announcements') },
+        :available_to => [
+          'StudentEnrollment',
+          'TaEnrollment',
+          'DesignerEnrollment',
+          'TeacherEnrollment',
+          'TeacherlessStudentEnrollment',
+          'ObserverEnrollment',
+          'AccountAdmin',
+          'AccountMembership'
+        ],
+        :true_for => [
+          'StudentEnrollment',
+          'TaEnrollment',
+          'DesignerEnrollment',
+          'ObserverEnrollment',
+          'TeacherEnrollment',
+          'AccountAdmin'
+        ]
+      },
       :send_messages => {
         :label => lambda { t('permissions.send_messages', "Send messages to individual course members") },
         :available_to => [

db/migrate/20160127184059_populate_announcement_permissions.rb

@@ -0,0 +1,10 @@
+class PopulateAnnouncementPermissions < ActiveRecord::Migration
+  tag :postdeploy
+
+  def up
+    DataFixup::AddRoleOverridesForNewPermission.send_later_if_production(:run, :view_forum, :view_announcements)
+  end
+
+  def down
+  end
+end