mute assignments through the api

test plan:

 * create an assignment using the muted flag = true. It should be muted
 * update this assignment using the muted flag = false. It should not be muted
 * update this assignment without using the muted flag. It should not be muted

 * create an assignment using the muted flag = false. It should not be muted
 * update this assignment using the muted flag = true. It should be muted.
 * update this assignment without using the muted flag. It should be muted.

Change-Id: I07d1a83dc3cbbcb203ba4454f5d888b453898d7f
Reviewed-on: https://gerrit.instructure.com/16790
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>

app/controllers/assignments_api_controller.rb

@@ -369,6 +369,12 @@ class AssignmentsApiController < ApplicationController
   #   The assignment group id to put the assignment in.
   #   Defaults to the top assignment group in the course.
   #
+  # @argument assignment[muted] [Boolean]
+  #   Whether this assignment is muted.
+  #   A muted assignment does not send change notifications
+  #   and hides grades from students.
+  #   Defaults to false.
+  #
   # @argument assignment[assignment_overrides] [Optional, [AssignmentOverride]]
   #   List of overrides for the assignment.
   #   NOTE: The assignment overrides feature is in beta.

lib/api/v1/assignment.rb

@@ -194,6 +194,8 @@ module Api::V1::Assignment
       update_params["group_category_id"] = gc.try(:id)
     end
 
+    assignment.muted = value_to_boolean(assignment_params["muted"]) if assignment_params.key? "muted"
+
     # do some fiddling with due_at for fancy midnight and add to update_params
     if update_params.has_key?("due_at")
       update_params["time_zone_edited"] = Time.zone.name

spec/apis/v1/assignments_api_spec.rb

@@ -178,7 +178,8 @@ describe AssignmentsApiController, :type => :integration do
                 'test_custom' => {
                   'value' => '1'
                 }
-              }
+              },
+              'muted' => 'true'
             }
        )
       @group_category.reload
@@ -189,7 +190,7 @@ describe AssignmentsApiController, :type => :integration do
       @json['name'].should == 'some assignment'
       @json['course_id'].should == @course.id
       @json['description'].should == 'assignment description'
-      @json['muted'].should == false
+      @json['muted'].should == true
       @json['lock_at'].should == @assignment.lock_at.iso8601
       @json['unlock_at'].should == @assignment.unlock_at.iso8601
       @json['automatic_peer_reviews'].should == true 
@@ -401,9 +402,9 @@ describe AssignmentsApiController, :type => :integration do
         @json['description'].should == 'assignment description'
       end
 
-      it "does not update the assignment's muted property" do
-        @assignment.muted?.should == false
-        @json['muted'].should == false
+      it "updates the assignment's muted property" do
+        @assignment.muted?.should == true
+        @json['muted'].should == true
       end
 
       it "updates the assignment's position" do