feat: Add duplicate button when a transaction is selected (#1123)

* feat: Add duplicate button when a transaction is selected

* feat: add merchant field

* feat: add duplicate transaction btn 2

test/controllers/transactions_controller_test.rb

@@ -309,6 +309,38 @@ end
     assert_not entry.protected_from_sync?
   end
 
+  test "new with duplicate_entry_id pre-fills form from source transaction" do
+    @entry.reload
+
+    get new_transaction_url(duplicate_entry_id: @entry.id)
+    assert_response :success
+    assert_select "input[name='entry[name]'][value=?]", @entry.name
+    assert_select "input[type='number'][name='entry[amount]']" do |elements|
+      assert_equal sprintf("%.2f", @entry.amount.abs), elements.first["value"]
+    end
+    assert_select "input[type='hidden'][name='entry[entryable_attributes][merchant_id]']"
+  end
+
+  test "new with invalid duplicate_entry_id renders empty form" do
+    get new_transaction_url(duplicate_entry_id: -1)
+    assert_response :success
+    assert_select "input[name='entry[name]']" do |elements|
+      assert_nil elements.first["value"]
+    end
+  end
+
+  test "new with duplicate_entry_id from another family does not prefill form" do
+    other_family = families(:empty)
+    other_account = other_family.accounts.create!(name: "Other", balance: 0, currency: "USD", accountable: Depository.new)
+    other_entry = create_transaction(account: other_account, name: "Should not leak", amount: 50)
+
+    get new_transaction_url(duplicate_entry_id: other_entry.id)
+    assert_response :success
+    assert_select "input[name='entry[name]']" do |elements|
+      assert_nil elements.first["value"]
+    end
+  end
+
   test "unlock clears import_locked flag" do
     family = families(:empty)
     sign_in users(:empty)