individual: raise when the individual object cannot be created

Currently, a number of dossiers in production are for procedures for
individuals, but don't have a `individual` object.

This is probably because creating the Individual from France Connect
infos fails – but fails quietly, and nullify the relationship.

As a first step, we now raise an exception when the creation from FC
infos fails. We will then identify the issue, and see if we can fix it –
or if we should be resilient to this kind of issues.

app/models/individual.rb

@@ -10,7 +10,7 @@ class Individual < ApplicationRecord
   GENDER_FEMALE = 'Mme'
 
   def self.create_from_france_connect(fc_information)
-    create(
+    create!(
       nom: fc_information.family_name,
       prenom: fc_information.given_name,
       gender: fc_information.gender == 'female' ? GENDER_FEMALE : GENDER_MALE