Add local authority links

app/models/local_authority.rb

@@ -1,4 +1,7 @@
 class LocalAuthority < ApplicationRecord
+  has_many :local_authority_links, dependent: :destroy
+  has_many :linked_local_authorities, class_name: "LocalAuthority", through: :local_authority_links
+
   scope :active, ->(date) { where("start_date <= ? AND (end_date IS NULL OR end_date >= ?)", date, date) }
   scope :england, -> { where("code LIKE ?", "E%") }
 end

app/models/local_authority_link.rb

@@ -0,0 +1,4 @@
+class LocalAuthorityLink < ApplicationRecord
+  belongs_to :local_authority, class_name: "LocalAuthority"
+  belongs_to :linked_local_authority, class_name: "LocalAuthority"
+end

db/migrate/20230309145740_add_local_authority_link.rb

@@ -0,0 +1,12 @@
+class AddLocalAuthorityLink < ActiveRecord::Migration[7.0]
+  def change
+    create_table :local_authority_links do |t|
+      t.references :local_authority
+      t.references :linked_local_authority
+
+      t.timestamps
+    end
+    add_foreign_key :local_authority_links, :local_authorities, column: :local_authority_id
+    add_foreign_key :local_authority_links, :local_authorities, column: :linked_local_authority_id
+  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: 2023_03_08_101826) do
+ActiveRecord::Schema[7.0].define(version: 2023_03_09_145740) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -299,6 +299,15 @@ ActiveRecord::Schema[7.0].define(version: 2023_03_08_101826) do
     t.index ["code"], name: "index_local_authority_code", unique: true
   end
 
+  create_table "local_authority_links", force: :cascade do |t|
+    t.bigint "local_authority_id"
+    t.bigint "linked_local_authority_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["linked_local_authority_id"], name: "index_local_authority_links_on_linked_local_authority_id"
+    t.index ["local_authority_id"], name: "index_local_authority_links_on_local_authority_id"
+  end
+
   create_table "location_deactivation_periods", force: :cascade do |t|
     t.datetime "deactivation_date"
     t.datetime "reactivation_date"
@@ -641,6 +650,8 @@ ActiveRecord::Schema[7.0].define(version: 2023_03_08_101826) do
   add_foreign_key "lettings_logs", "locations"
   add_foreign_key "lettings_logs", "organisations", column: "owning_organisation_id", on_delete: :cascade
   add_foreign_key "lettings_logs", "schemes"
+  add_foreign_key "local_authority_links", "local_authorities"
+  add_foreign_key "local_authority_links", "local_authorities", column: "linked_local_authority_id"
   add_foreign_key "locations", "schemes"
   add_foreign_key "organisation_relationships", "organisations", column: "child_organisation_id"
   add_foreign_key "organisation_relationships", "organisations", column: "parent_organisation_id"