Add Carte champs support to the API

app/serializers/champs/carte_champ_serializer.rb

@@ -0,0 +1,11 @@
+class Champs::CarteChampSerializer < ChampSerializer
+  has_many :geo_areas
+
+  def value
+    if object.value.present?
+      JSON.parse(object.value)
+    else
+      nil
+    end
+  end
+end

app/serializers/geo_area_serializer.rb

@@ -0,0 +1,16 @@
+class GeoAreaSerializer < ActiveModel::Serializer
+  attributes :geometry,
+    :source,
+    :surface_intersection,
+    :surface_parcelle,
+    :numero,
+    :feuille,
+    :section,
+    :code_dep,
+    :nom_com,
+    :code_com,
+    :code_arr,
+    :code,
+    :nom,
+    :commune
+end