Add join table for organisation self-referential parent/child relationships

app/models/organisation.rb

@@ -6,6 +6,10 @@ class Organisation < ApplicationRecord
   has_many :organisation_rent_periods
   has_many :owned_schemes, class_name: "Scheme", foreign_key: "owning_organisation_id", dependent: :delete_all
   has_many :managed_schemes, class_name: "Scheme", foreign_key: "managing_organisation_id"
+  has_many :parent_organisation_relationships, foreign_key: :child_organisation_id, class_name: "OrganisationRelationship"
+  has_many :parent_organisations, through: :parent_organisation_relationships
+  has_many :child_organisation_relationships, foreign_key: :parent_organisation_id, class_name: "OrganisationRelationship"
+  has_many :child_organisations, through: :child_organisation_relationships
 
   scope :search_by_name, ->(name) { where("name ILIKE ?", "%#{name}%") }
   scope :search_by, ->(param) { search_by_name(param) }

app/models/organisation_relationship.rb

@@ -0,0 +1,4 @@
+class OrganisationRelationship < ApplicationRecord
+  belongs_to :child_organisation, class_name: "Organisation"
+  belongs_to :parent_organisation, class_name: "Organisation"
+end

db/migrate/20220810152340_add_parent_child_relationships.rb

@@ -0,0 +1,9 @@
+class AddParentChildRelationships < ActiveRecord::Migration[7.0]
+  def change
+    create_table :organisation_relationships do |t|
+      t.integer :child_organisation_id, foreign_key: true
+      t.integer :parent_organisation_id, foreign_key: true
+      t.timestamps
+    end
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2022_08_02_125711) do
+ActiveRecord::Schema[7.0].define(version: 2022_08_10_152340) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -263,6 +263,13 @@ ActiveRecord::Schema[7.0].define(version: 2022_08_02_125711) do
     t.boolean "empty_export", default: false, null: false
   end
 
+  create_table "organisation_relationships", force: :cascade do |t|
+    t.integer "child_organisation_id"
+    t.integer "parent_organisation_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+  end
+
   create_table "organisation_rent_periods", force: :cascade do |t|
     t.bigint "organisation_id"
     t.integer "rent_period"