add unread conversation count api endpoint

fixes CNVS-5780

test plan
- ensure that /api/v1/conversations/unread_count correctly reports
 a user's unread conversation message count

Change-Id: I9999b5c43b249c1db1ca003d84b1e06c7ac9e434
Reviewed-on: https://gerrit.instructure.com/20769
Reviewed-by: Jon Willesen <jonw@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Adam Phillipps <adam@instructure.com>
Product-Review: Joel Hough <joel@instructure.com>

app/controllers/conversations_controller.rb

@@ -604,6 +604,15 @@ class ConversationsController < ApplicationController
   # Deprecated, see the {api:SearchController#recipients Find recipients endpoint} in the Search API
   def find_recipients; end
 
+  # @API Unread count
+  # Get the number of unread conversations for the current user
+  #
+  # @example_response
+  #   {'unread_count': '7'}
+  def unread_count
+    render(:json => {'unread_count' => @current_user.unread_conversations_count.to_json})
+  end
+  
   def public_feed
     return unless get_feed_context(:only => [:user])
     @current_user = @context

config/routes.rb

@@ -927,6 +927,7 @@ ActionController::Routing::Routes.draw do |map|
       conversations.post 'conversations', :action => :create
       conversations.post 'conversations/mark_all_as_read', :action => :mark_all_as_read
       conversations.get 'conversations/batches', :action => :batches, :path_name => 'conversations_batches'
+      conversations.get 'conversations/unread_count', :action => :unread_count
       conversations.get 'conversations/:id', :action => :show
       conversations.put 'conversations/:id', :action => :update # stars, subscribed-ness, workflow_state
       conversations.delete 'conversations/:id', :action => :destroy

spec/apis/v1/conversations_api_spec.rb

@@ -1469,4 +1469,13 @@ describe ConversationsController, :type => :integration do
     end
   end
 
+  describe 'unread_count' do
+    it 'should return the number of unread conversations for the current user' do
+      conversation(student_in_course, :workflow_state => 'unread')
+      json = api_call(:get, '/api/v1/conversations/unread_count.json',
+                      {:controller => 'conversations', :action => 'unread_count', :format => 'json'})
+      json.should eql({'unread_count' => '1'})
+    end
+  end
+  
 end