small changes to models

app/models/organisation.rb

@@ -2,7 +2,7 @@ class Organisation < ApplicationRecord
   has_many :users, dependent: :delete_all
   has_many :data_protection_officers, -> { where(is_dpo: true) }, class_name: "User"
   has_one :data_protection_confirmation
-  has_many :organisation_rent_periods
+  has_many :organisation_rent_periods, dependent: :destroy
   has_many :owned_schemes, class_name: "Scheme", foreign_key: "owning_organisation_id", dependent: :delete_all
   has_many :parent_organisation_relationships, foreign_key: :child_organisation_id, class_name: "OrganisationRelationship"
   has_many :parent_organisations, through: :parent_organisation_relationships

app/models/organisation_rent_period.rb

@@ -1,3 +1,5 @@
 class OrganisationRentPeriod < ApplicationRecord
   belongs_to :organisation
+
+  validates :organisation_id, uniqueness: { scope: :rent_period } # rubocop:disable Rails/UniqueValidationWithoutIndex
 end