IIRR-31(puzzle): Add original_puzzle reference for clones

Added original_puzzle association to Puzzle model and migration to
support tracking the source of cloned puzzles. Updated clone controller
and tests to set and verify original_puzzle_id on clone creation.

Will be handy when we want to calculate how many people got it right or
wrong, if we ever want to show stats for the puzzles.

Ref: https://ombulabs.atlassian.net/browse/IIRR-31

Author: fbuys

app/controllers/puzzles/clones_controller.rb

@@ -2,7 +2,7 @@ class Puzzles::ClonesController < ApplicationController
   def create
     original_puzzle = Puzzle.find(params[:puzzle_id])
     attributes = original_puzzle.attributes.slice("question", "answer", "explanation", "link", "suggested_by")
-    cloned_puzzle = Puzzle.new(attributes.merge(state: params.fetch(:state, "pending")))
+    cloned_puzzle = Puzzle.new(attributes.merge(original_puzzle:, state: params.fetch(:state, "pending")))
 
     if cloned_puzzle.save
       redirect_to puzzles_path, notice: "Puzzle cloned. You can now edit the new puzzle."

app/models/puzzle.rb

@@ -3,6 +3,8 @@ class Puzzle < ApplicationRecord
   enum :state, { approved: 0, rejected: 1, pending: 2, archived: 3 }
   has_many :answers
 
+  belongs_to :original_puzzle, class_name: "Puzzle", optional: true
+
   validates :question, presence: true
 
   scope :archived, -> { where(state: :archived).order(sent_at: :desc) }

db/migrate/20260130200200_add_original_puzzle_to_puzzles_table.rb

@@ -0,0 +1,5 @@
+class AddOriginalPuzzleToPuzzlesTable < ActiveRecord::Migration[8.0]
+  def change
+    add_reference :puzzles, :original_puzzle, foreign_key: { to_table: :puzzles }, index: true, null: true
+  end
+end

db/schema.rb

@@ -12,6 +12,7 @@ class Puzzles::ClonesControllerTest < ActionDispatch::IntegrationTest
     cloned = Puzzle.order(:id).last
     assert_redirected_to puzzles_path
 
+    assert_equal original.id, cloned.original_puzzle_id
     assert_equal original.question, cloned.question
     assert_equal original.answer, cloned.answer
     assert_equal original.explanation, cloned.explanation