conditionally allow total pages on account_courses endpoint

test plan
 - last_page should be nil for account_courses endpoint
 - with setting set, it should not be nil
 - see specs, they should pass

fixes VICE-1996
flag=none

Change-Id: Ibaf8aff044650f6c0ffcc7f7ccbd8fa99cd53e0d
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/272598
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Matthew Lemon <mlemon@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>

app/controllers/accounts_controller.rb

@@ -740,7 +740,9 @@ def courses_api
 
     page_opts = {}
     # don't calculate a total count for this endpoint.
-    page_opts[:total_entries] = nil
+    if params[:search_term] || !@account.allow_last_page_on_account_courses?
+      page_opts[:total_entries] = nil
+    end
 
     all_precalculated_permissions = nil
     GuardRail.activate(:secondary) do

app/models/account.rb

@@ -354,6 +354,7 @@ def resolved_outcome_calculation_method
   # push notifications which may be routed through US datacenters by Google/Apple
   add_setting :enable_push_notifications, boolean: true, root_only: true, default: true
   add_setting :allow_last_page_on_course_users, boolean: true, root_only: true, default: false
+  add_setting :allow_last_page_on_account_courses, boolean: true, root_only: true, default: false
 
   def settings=(hash)
     if hash.is_a?(Hash) || hash.is_a?(ActionController::Parameters)

spec/controllers/accounts_controller_spec.rb

@@ -1223,6 +1223,16 @@ def admin_logged_in(account)
       expect(response.headers.to_a.find { |a| a.first == "Link" }.last).to_not include("last")
     end
 
+    it "should set pagination total_pages/last page link if account setting is set" do
+      @account.settings[:allow_last_page_on_account_courses] = true
+      @account.save!
+      admin_logged_in(@account)
+      get 'courses_api', params: {:account_id => @account.id, per_page: 1}
+
+      expect(response).to be_successful
+      expect(response.headers.to_a.find { |a| a.first == "Link" }.last).to include("last")
+    end
+
     it "should properly remove sections from includes" do
       @s1 = @course.course_sections.create!
       @course.enroll_student(user_factory(:active_all => true), :section => @s1, :allow_multiple_enrollments => true)