add user id to user sort clause

so we still have a deterministic sort for pagination when
multiple users have the same sortable name

fixes CNVS-36604

Change-Id: I75b5eaae782553a80a185660ddb4346dbe79f853
Reviewed-on: https://gerrit.instructure.com/110288
Tested-by: Jenkins
Reviewed-by: James Williams  <jamesw@instructure.com>
QA-Review: Deepeeca Soundarrajan <dsoundarrajan@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>

app/models/user.rb

@@ -240,6 +240,7 @@ class User < ActiveRecord::Base
   def self.order_by_sortable_name(options = {})
     order_clause = clause = sortable_name_order_by_clause
     order_clause = "#{clause} DESC" if options[:direction] == :descending
+    order_clause += ",users.id"
     scope = self.order(order_clause)
     if scope.select_values.empty?
       scope = scope.select(self.arel_table[Arel.star])

spec/models/user_spec.rb

@@ -2123,6 +2123,11 @@ describe User do
       expect(User.sortable_name_order_by_clause).not_to match(/'es'/)
       expect(User.sortable_name_order_by_clause).to match(/'root'/)
     end
+
+    it "breaks ties with user id" do
+      ids = 5.times.map { User.create!(:name => "Abcde").id }.sort
+      expect(User.order_by_sortable_name.where(id: ids).map(&:id)).to eq(ids)
+    end
   end
 
   describe "quota" do