amelioration(champs.epci): passe le champs epci au DSFR et l'encapsule dans un fieldset

app/components/editable_champ/epci_component/epci_component.html.haml

@@ -1,5 +1,9 @@
-%label.notice{ for: @champ.code_departement_input_id } Le département de l’EPCI
+.fr-fieldset__element
-= @form.select :code_departement, departement_options, departement_select_options, required: @champ.required?, id: @champ.code_departement_input_id, class: "width-33-desktop width-100-mobile fr-select"
+  = @form.label "Le département de l’EPCI", for: @champ.code_departement_input_id, class: 'fr-label'
+  = @form.select :code_departement, departement_options, departement_select_options, required: @champ.required?, id: @champ.code_departement_input_id, class: "width-33-desktop width-100-mobile fr-select"
+
 - if @champ.departement?
-  = @form.label "EPCI", for: @champ.epci_input_id
+  .fr-fieldset__element
+    .fr-select-group
+      = @form.label "EPCI", for: @champ.epci_input_id, class: 'fr-label'
       = @form.select :value, epci_options, epci_select_options, required: @champ.required?, id: @champ.epci_input_id, aria: { describedby: @champ.describedby_id }, class: "width-33-desktop width-100-mobile fr-select"

app/models/champs/epci_champ.rb

@@ -22,6 +22,18 @@ class Champs::EpciChamp < Champs::TextChamp
     code_departement.present?
   end
 
+  def dsfr_champ_container
+    :fieldset
+  end
+
+  def html_label?
+    false
+  end
+
+  def legend_label?
+    true
+  end
+
   def code?
     code.present?
   end