fix(a11y/attachment): associate input to label, no empty id

app/components/attachment/edit_component.rb

@@ -132,9 +132,8 @@ class Attachment::EditComponent < ApplicationComponent
 
   def input_id
     if champ.present?
-      # Single or first attachment input must match label "for" attribute. Others must remain unique.
-      return champ.input_id if @index.zero?
-      return "#{champ.input_id}_#{attachment_id}"
+      # There is always a single input by champ, its id must match the label "for" attribute.
+      return champ.input_id
     end
 
     helpers.field_id(@attached_file.record, attribute_name)

app/components/attachment/edit_component/edit_component.html.haml

@@ -1,4 +1,4 @@
-.attachment.fr-upload-group{ id: attachment ? dom_id(attachment, :edit) : nil, class: class_names("fr-mb-2w": !(as_multiple? && downloadable?)) }
+.attachment.fr-upload-group{ { id: attachment ? dom_id(attachment, :edit) : nil, class: class_names("fr-mb-2w": !(as_multiple? && downloadable?)) }.compact }
   - if persisted?
     %div{ id: dom_id(attachment, :persisted_row) }
       .flex.flex-gap-2{ class: class_names("attachment-error": attachment.virus_scanner_error?) }