dossier: fix upload route of piece_justificative in repetitions

In repetitions, `form.index` doesn't make much sense. Turns out we
don't really need the index of the champ: we can just use the champ id.

app/helpers/champ_helper.rb

@@ -34,7 +34,7 @@ module ChampHelper
 
   def auto_attach_url(form, object)
     if feature_enabled?(:autoupload_dossier_attachments) && object.is_a?(Champ) && object.public?
-      champs_piece_justificative_url(form.index)
+      champs_piece_justificative_url(object.id)
     end
   end
 end

app/javascript/new_design/dossiers/auto-upload-controller.js

@@ -70,7 +70,7 @@ export default class AutoUploadController {
     const attachmentRequest = {
       url: autoAttachUrl,
       type: 'PUT',
-      data: `champ_id=${champId}&blob_signed_id=${blobSignedId}`
+      data: `blob_signed_id=${blobSignedId}`
     };
     await ajax(attachmentRequest);
 

config/routes.rb

@@ -121,7 +121,7 @@ Rails.application.routes.draw do
     get ':position/dossier_link', to: 'dossier_link#show', as: :dossier_link
     post ':position/carte', to: 'carte#show', as: :carte
     post ':position/repetition', to: 'repetition#show', as: :repetition
-    put ':position/piece_justificative', to: 'piece_justificative#update', as: :piece_justificative
+    put 'piece_justificative/:champ_id', to: 'piece_justificative#update', as: :piece_justificative
   end
 
   get 'attachments/:id', to: 'attachments#show', as: :attachment