Use a dedicated resource for showing cards in draft mode

Mobile team needs this. Also, this lets us get rid from some conditionals for handling
both modes with a single template.

https://3.basecamp.com/2914079/buckets/44843469/messages/9437287330

test/controllers/cards_controller_test.rb

@@ -21,7 +21,7 @@ class CardsControllerTest < ActionDispatch::IntegrationTest
     end
 
     card = Card.last
-    assert_redirected_to card
+    assert_redirected_to card_draft_path(card)
 
     assert card.drafted?
   end
@@ -31,10 +31,17 @@ class CardsControllerTest < ActionDispatch::IntegrationTest
 
     assert_no_difference -> { Card.count } do
       post board_cards_path(boards(:writebook))
-      assert_redirected_to draft
+      assert_redirected_to card_draft_path(draft)
     end
   end
 
+  test "show redirects to draft when card is drafted" do
+    card = boards(:writebook).cards.create!(creator: users(:kevin), status: :drafted)
+
+    get card_path(card)
+    assert_redirected_to card_draft_path(card)
+  end
+
   test "show" do
     get card_path(cards(:logo))
     assert_response :success