Fix for bug in Plan duplication results in original plan identifier being 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.

Author: John Pinto

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog
 
+### Fixed 
+- Fixed a bug in the deep copy of plans where the old identifier was being copied into the new plan. We now copy the generated id of the new plan to the identifier field.
+
 ## v4.2.0
 
 **Note this upgrade is mainly a migration from Bootstrap 3 to Bootstrap 5.** 

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