Add indexed_by=maybe to cards (#2827)

* Add indexed_by=maybe to cards

test/controllers/cards_controller_test.rb

@@ -29,6 +29,13 @@ class CardsControllerTest < ActionDispatch::IntegrationTest
     assert_equal [ cards(:logo).number, cards(:layout).number, cards(:text).number ].sort, @response.parsed_body.pluck("number").sort
   end
 
+  test "index as JSON can filter by maybe index" do
+    get cards_path(format: :json), params: { indexed_by: "maybe" }
+    assert_response :success
+
+    assert_equal [ cards(:buy_domain).number ], @response.parsed_body.pluck("number")
+  end
+
   test "create a new draft" do
     assert_difference -> { Card.count }, 1 do
       post board_cards_path(boards(:writebook))