Fix for bug in Plan duplication results in original plan identifier b…

…eing copied.

Change in class method Plan.deep_copy:
  - Firstly, on duplicating the Plan we set the plan identifier to nil and save.
  - Then we fill the identifier variable with the Plan id that was
      regenerated when the duplicate copy was save in the previous.
  - We then persist this change by saving the Plan again.

app/models/plan.rb

@@ -254,7 +254,12 @@ def self.deep_copy(plan)
     plan_copy = plan.dup
     plan_copy.title = "Copy of #{plan.title}"
     plan_copy.feedback_requested = false
+    # Don't copy the identifier as it will be regenerated
+    plan_copy.identifier = nil
     plan_copy.save!
+    # Copy newly generated Id to the identifier
+    plan_copy.identifier = plan_copy.id
+    plan.save!
     plan.answers.each do |answer|
       answer_copy = Answer.deep_copy(answer)
       answer_copy.plan_id = plan_copy.id