Extract error_id

To DRY up helper methods and error_summary partial.

Co-authored-by: James Mead <3169+floehopper@users.noreply.github.com>

app/helpers/application_helper.rb

@@ -30,7 +30,7 @@ def govuk_fieldset_with_optional_error(journey, attribute)
     error = journey.errors[attribute].first
 
     options = { class: 'govuk-fieldset' }
-    options['aria-describedby'] = "#{attribute}-error" if error.present?
+    options['aria-describedby'] = error_id(attribute) if error.present?
 
     content_tag :fieldset, options do
       yield
@@ -41,7 +41,7 @@ def display_error(journey, attribute)
     error = journey.errors[attribute].first
     return if error.blank?
 
-    content_tag :span, id: "#{attribute}-error", class: 'govuk-error-message' do
+    content_tag :span, id: error_id(attribute), class: 'govuk-error-message' do
       error
     end
   end
@@ -53,4 +53,8 @@ def css_classes_for_input(journey, attribute, extra_classes = [])
     css_classes += ['govuk-input--error'] if error.present?
     css_classes
   end
+
+  def error_id(attribute)
+    "#{attribute}-error"
+  end
 end

app/views/journey/_error_summary.html.erb

@@ -7,7 +7,7 @@
       <ul class="govuk-list govuk-error-summary__list">
         <% errors.keys.each do |attribute| %>
           <li>
-            <a href="<%= "##{attribute}-error" %>"><%= errors[attribute].first %></a>
+            <a href="#<%= error_id(attribute) %>"><%= errors[attribute].first %></a>
           </li>
         <% end %>
       </ul>