Use interruption_screen? method (#1238)

More safe than checking whether the question included value_check in their name

app/models/form.rb

@@ -61,7 +61,7 @@ class Form
 
     page_ids = subsection_for_page(page).pages.map(&:id)
     page_index = page_ids.index(page.id)
-    page_id = if page.id.include?("value_check") && log[page.questions[0].id] == 1 && page.routed_to?(log, current_user)
+    page_id = if page.interruption_screen? && log[page.questions[0].id] == 1 && page.routed_to?(log, current_user)
                 previous_page(page_ids, page_index, log, current_user)
               else
                 page_ids[page_index + 1]

app/views/form/page.html.erb

@@ -44,7 +44,7 @@
       <%= f.hidden_field :page, value: @page.id %>
 
       <div class="govuk-button-group">
-        <% if !@page.id.include?("value_check") && if request.query_parameters["referrer"] != "check_answers" %>
+        <% if !@page.interruption_screen? && if request.query_parameters["referrer"] != "check_answers" %>
           <%= f.govuk_submit "Save and continue" %>
           <%= govuk_link_to "Skip for now", send(@log.form.next_page_redirect_path(@page, @log, current_user), @log) %>
           <% else %>