add account-level external tool resource_selection route

test plan:
* add an account-level external tool that adds an
editor button (e.g. 'Youtube', 'Trello')
* use the tinymce editor in an account-level context
(e.g. edit an account-level outcome description)
* click the editor button
* should not get a 'Page not found' error

fixes #CNVS-6714

Change-Id: I505963e61fc8180646dd829aaa2a5b9003b35ab0
Reviewed-on: https://gerrit.instructure.com/22106
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>

config/routes.rb

@@ -546,9 +546,11 @@ FakeRails3Routes.draw do
     match 'test_ldap_logins' => 'account_authorization_configs#test_ldap_login', :as => :test_ldap_logins
     match 'saml_testing' => 'account_authorization_configs#saml_testing', :as => :saml_testing
     match 'saml_testing_stop' => 'account_authorization_configs#saml_testing_stop', :as => :saml_testing_stop
+
     match 'external_tools/sessionless_launch' => 'external_tools#sessionless_launch', :as => :external_tools_sessionless_launch
     resources :external_tools do
       match 'finished' => 'external_tools#finished', :as => :finished
+      match 'resource_selection' => 'external_tools#resource_selection', :as => :resource_selection
     end
 
     concerns :chats

spec/controllers/external_tools_controller_spec.rb

@@ -110,6 +110,16 @@ describe ExternalToolsController do
       assigns[:tool_settings]['custom_canvas_enrollment_state'].should == 'active'
     end
 
+    it "should find account-level tools" do
+      @user = account_admin_user
+      user_session(@user)
+
+      tool = new_valid_tool(Account.default)
+      get 'resource_selection', :account_id => Account.default.id, :external_tool_id => tool.id
+      response.should be_success
+      assigns[:tool].should == tool
+    end
+
     it "should be accessible even after course is soft-concluded" do
       course_with_student_logged_in(:active_all => true)
       @course.conclude_at = 1.day.ago