refactor(dossier): explicitly build default values - less callbacks, less magic

app/controllers/api/public/v1/dossiers_controller.rb

@@ -9,7 +9,7 @@ class API::Public::V1::DossiersController < API::Public::V1::BaseController
       state: Dossier.states.fetch(:brouillon),
       prefilled: true
     )
-    dossier.build_default_individual
+    dossier.build_default_values
     if dossier.save
       dossier.prefill!(PrefillChamps.new(dossier, params.to_unsafe_h).to_a, PrefillIdentity.new(dossier, params.to_unsafe_h).to_h)
       render json: serialize_dossier(dossier), status: :created

app/controllers/users/commencer_controller.rb

@@ -127,7 +127,7 @@ module Users
         state: Dossier.states.fetch(:brouillon),
         prefilled: true
       )
-      @prefilled_dossier.build_default_individual
+      @prefilled_dossier.build_default_values
       if @prefilled_dossier.save
         @prefilled_dossier.prefill!(PrefillChamps.new(@prefilled_dossier, params.to_unsafe_h).to_a, PrefillIdentity.new(@prefilled_dossier, params.to_unsafe_h).to_h)
       end

app/controllers/users/dossiers_controller.rb

@@ -385,7 +385,7 @@ module Users
         user: current_user,
         state: Dossier.states.fetch(:brouillon)
       )
-      dossier.build_default_individual
+      dossier.build_default_values
       dossier.save!
       DossierMailer.with(dossier:).notify_new_draft.deliver_later