Add parks_by_state model

db/migrate/20251008150542_create_parks_by_states.rb

@@ -0,0 +1,14 @@
+class CreateParksByStates < ActiveRecord::Migration[8.0]
+  def change
+    create_table :parks_by_states do |t|
+      t.string :park_code, null: false
+      t.string :state, null: false
+
+      t.timestamps
+    end
+
+    add_index :parks_by_states, [:state, :park_code], unique: true
+    add_index :parks_by_states, :park_code
+    add_foreign_key :parks_by_states, :parks, column: :park_code, primary_key: :code
+  end
+end