models: explicitly mark optional belongs_to relationship as so

This prepares making the `belongs_to` relationship required by default.

app/models/avis.rb

@@ -18,7 +18,7 @@ class Avis < ApplicationRecord
   include EmailSanitizableConcern
 
   belongs_to :dossier, inverse_of: :avis, touch: true
-  belongs_to :instructeur
+  belongs_to :instructeur, optional: true
   belongs_to :claimant, class_name: 'Instructeur'
 
   has_one_attached :piece_justificative_file

app/models/champ.rb

@@ -17,14 +17,14 @@
 class Champ < ApplicationRecord
   belongs_to :dossier, -> { with_discarded }, inverse_of: :champs, touch: true
   belongs_to :type_de_champ, inverse_of: :champ
-  belongs_to :parent, class_name: 'Champ'
+  belongs_to :parent, class_name: 'Champ', optional: true
   has_many :commentaires
   has_one_attached :piece_justificative_file
 
   # We declare champ specific relationships (Champs::CarteChamp, Champs::SiretChamp and Champs::RepetitionChamp)
   # here because otherwise we can't easily use includes in our queries.
   has_many :geo_areas, dependent: :destroy
-  belongs_to :etablissement, dependent: :destroy
+  belongs_to :etablissement, optional: true, dependent: :destroy
   has_many :champs, -> { ordered }, foreign_key: :parent_id, inverse_of: :parent, dependent: :destroy
 
   delegate :libelle,

app/models/commentaire.rb

@@ -14,8 +14,8 @@
 class Commentaire < ApplicationRecord
   belongs_to :dossier, inverse_of: :commentaires, touch: true
 
-  belongs_to :user
-  belongs_to :instructeur
+  belongs_to :user, optional: true
+  belongs_to :instructeur, optional: true
 
   validate :messagerie_available?, on: :create
 

app/models/etablissement.rb

@@ -47,7 +47,7 @@
 #  entreprise_id                            :integer
 #
 class Etablissement < ApplicationRecord
-  belongs_to :dossier
+  belongs_to :dossier, optional: true
 
   has_one :champ, class_name: 'Champs::SiretChamp'
   has_many :exercices, dependent: :destroy

app/models/france_connect_information.rb

@@ -15,7 +15,7 @@
 #  user_id                       :integer
 #
 class FranceConnectInformation < ApplicationRecord
-  belongs_to :user
+  belongs_to :user, optional: true
 
   validates :france_connect_particulier_id, presence: true, allow_blank: false, allow_nil: false
 end

app/models/invite.rb

@@ -15,7 +15,7 @@ class Invite < ApplicationRecord
   include EmailSanitizableConcern
 
   belongs_to :dossier
-  belongs_to :user
+  belongs_to :user, optional: true
 
   before_validation -> { sanitize_email(:email) }
 

app/models/procedure.rb

@@ -66,9 +66,9 @@ class Procedure < ApplicationRecord
   has_one :module_api_carto, dependent: :destroy
   has_one :attestation_template, dependent: :destroy
 
-  belongs_to :parent_procedure, class_name: 'Procedure'
-  belongs_to :canonical_procedure, class_name: 'Procedure'
-  belongs_to :service
+  belongs_to :parent_procedure, class_name: 'Procedure', optional: true
+  belongs_to :canonical_procedure, class_name: 'Procedure', optional: true
+  belongs_to :service, optional: true
 
   def active_revision
     brouillon? ? draft_revision : published_revision

app/models/type_de_champ.rb

@@ -52,7 +52,7 @@ class TypeDeChamp < ApplicationRecord
   belongs_to :procedure
   belongs_to :revision, class_name: 'ProcedureRevision', optional: true
 
-  belongs_to :parent, class_name: 'TypeDeChamp'
+  belongs_to :parent, class_name: 'TypeDeChamp', optional: true
   has_many :types_de_champ, -> { ordered }, foreign_key: :parent_id, class_name: 'TypeDeChamp', inverse_of: :parent, dependent: :destroy
 
   store_accessor :options, :cadastres, :quartiers_prioritaires, :parcelles_agricoles, :old_pj, :drop_down_options, :skip_pj_validation

app/models/user.rb

@@ -45,8 +45,8 @@ class User < ApplicationRecord
   has_many :dossiers_invites, through: :invites, source: :dossier
   has_many :feedbacks, dependent: :destroy
   has_one :france_connect_information, dependent: :destroy
-  belongs_to :instructeur
-  belongs_to :administrateur
+  belongs_to :instructeur, optional: true
+  belongs_to :administrateur, optional: true
 
   accepts_nested_attributes_for :france_connect_information