Fix user_account_associations update for a restored enrollment

Test Plan
1) enroll a User in a Course
2) remove them from the Course
3) re-add them to Course
* verify the User has a corresponding user_account_association again

Change-Id: I37534ed332a964e65346976941ab0629847f316c
Reviewed-on: https://gerrit.instructure.com/75433
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins
QA-Review: August Thornton <august@instructure.com>
Product-Review: Tyson Brown <tbrown@instructure.com>

Author: Tyson Brown

app/models/enrollment.rb

@@ -316,7 +316,7 @@ def should_update_user_account_association?
 
   def update_user_account_associations_if_necessary
     return if self.fake_student?
-    if id_was.nil?
+    if id_was.nil? || (workflow_state_changed? && workflow_state_was == 'deleted')
       return if %w{creation_pending deleted}.include?(self.user.workflow_state)
       associations = User.calculate_account_associations_from_accounts([self.course.account_id, self.course_section.course.account_id, self.course_section.nonxlist_course.try(:account_id)].compact.uniq)
       self.user.update_account_associations(:incremental => true, :precalculated_associations => associations)

spec/models/enrollment_spec.rb

@@ -2053,4 +2053,19 @@ def enrollment_dates_override_test
       expect(@enrollment.readable_state_based_on_date).to eq :completed
     end
   end
+
+  describe "update user account associations if necessary" do
+    it "should create a user_account_association when restoring a deleted enrollment" do
+      sub_account = Account.default.sub_accounts.create!
+      course = Course.create!(:account => sub_account)
+      @enrollment = course.enroll_student(user)
+      expect(@user.user_account_associations.where(account: sub_account).exists?).to eq true
+
+      @enrollment.destroy
+      expect(@user.user_account_associations.where(account: sub_account).exists?).to eq false
+
+      @enrollment.restore
+      expect(@user.user_account_associations.where(account: sub_account).exists?).to eq true
+    end
+  end
 end