ISAICP-4124: Ensure that files in custom pages are displayed.

tests/features/custom_page/add_custom_page.feature

@@ -68,9 +68,16 @@ Feature: "Add custom page" visibility options.
     When I fill in the following:
       | Title | About us                      |
     And I enter "We are open about everything!" in the "Body" wysiwyg editor
+    And I attach the file "test.zip" to "Add a new file"
+    And I press "Upload"
+    # The "Description" field is the description of the file.
+    And I fill in "Description" with "Test file"
     And I press "Save"
     Then I should see the heading "About us"
     And I should see the success message "Custom page About us has been created."
+    And I should see the text "Attachments"
+    # The description of the file is set as the text to display.
+    And I should see the link "Test file"
     And the "Open Collective" collection should have a custom page titled "About us"
     # Check that the link to the custom page is visible on the collection page.
     When I go to the homepage of the "Open Collective" collection