Fix includes on api queries

app/models/champ.rb

@@ -5,6 +5,11 @@ class Champ < ApplicationRecord
   has_one_attached :piece_justificative_file
   has_one :virus_scan
 
+  # We declare champ specific relationships (Champs::CarteChamp and Champs::SiretChamp)
+  # here because otherwise we can't easily use includes in our queries.
+  has_many :geo_areas, dependent: :destroy
+  belongs_to :etablissement, dependent: :destroy
+
   delegate :libelle, :type_champ, :order_place, :mandatory?, :description, :drop_down_list, to: :type_de_champ
 
   scope :updated_since?, -> (date) { where('champs.updated_at > ?', date) }

app/models/champs/carte_champ.rb

@@ -1,6 +1,4 @@
 class Champs::CarteChamp < Champ
-  has_many :geo_areas, foreign_key: :champ_id, dependent: :destroy
-
   # We are not using scopes here as we want to access
   # the following collections on unsaved records.
   def cadastres

app/models/champs/siret_champ.rb

@@ -37,7 +37,6 @@ class Champs::SiretChamp < Champ
     ]
   ]
 
-  belongs_to :etablissement, dependent: :destroy
   accepts_nested_attributes_for :etablissement, allow_destroy: true, update_only: true
 
   def search_terms