procedures: group new_from_existing list by organization

As procedures are not grouped by Service (which are unique to an
administrator) but by organization, this allows procedures with the same
organization name to be displayed together.

app/models/procedure.rb

@@ -152,6 +152,10 @@ class Procedure < ApplicationRecord
     libelle.parameterize.first(50)
   end
 
+  def organisation_name
+    service&.nom || organisation
+  end
+
   def types_de_champ_ordered
     types_de_champ.order(:order_place)
   end