add attachment when instructor asking for a review

app/views/instructeurs/shared/avis/_form.html.haml

@@ -5,6 +5,12 @@
   = form_for avis, url: url, html: { class: 'form' } do |f|
     = f.email_field :emails, placeholder: 'Adresses email, séparées par des virgules', required: true, multiple: true, onchange: "javascript:DS.replaceSemicolonByComma(event);"
     = f.text_area :introduction, rows: 3, value: avis.introduction || 'Bonjour, merci de me donner votre avis sur ce dossier.', required: true
+    %p.tab-title Ajouter une pièce jointe
+    .form-group
+      = render 'shared/attachment/edit',
+        { form: f,
+        attached_file: avis.introduction_file,
+        user_can_destroy: true }
 
     - if linked_dossiers.present?
       = f.check_box :invite_linked_dossiers, {}, true, false