Fix duplicate HTML ID in document fields

Using `dom_id` means generating `new_document` as ID for new documents.
Since there might be more than one new document in the form, that means
duplicate IDs, which is invalid HTML.

Even though this issue doesn't affect image fields (because we don't
have many images on the same form), we're removing the ID there as well
for consistency.

app/components/documents/fields_component.html.erb

@@ -1,4 +1,4 @@
-<div id="<%= dom_id(document) %>" class="document direct-upload document-fields nested-fields">
+<div class="document direct-upload document-fields nested-fields">
   <%= f.hidden_field :id %>
   <%= f.hidden_field :user_id, value: current_user.id %>
   <%= f.hidden_field :cached_attachment %>

app/components/images/fields_component.html.erb

@@ -1,4 +1,4 @@
-<div id="<%= dom_id(image) %>" class="image direct-upload nested-fields">
+<div class="image direct-upload nested-fields">
   <%= f.hidden_field :id %>
   <%= f.hidden_field :user_id, value: current_user.id %>
   <%= f.hidden_field :cached_attachment %>

spec/shared/system/nested_documentable.rb

@@ -320,7 +320,7 @@ end
 def documentable_attach_new_file(path, success = true)
   click_link "Add new document"
 
-  document = all("#new_document").last
+  document = all(".document").last
   document_input = document.find("input[type=file]", visible: :hidden)
   attach_file(document_input[:id], path, make_visible: true)