feat: add special education disaggregation

db/migrate/20231004191828_create_speds.rb

@@ -0,0 +1,12 @@
+class CreateSpeds < ActiveRecord::Migration[7.0]
+  def change
+    create_table :speds do |t|
+      t.string :designation
+      t.string :slug
+
+      t.timestamps
+    end
+
+    add_index :speds, :designation
+  end
+end

db/migrate/20231004211430_add_sped_to_survey_item_response.rb

@@ -0,0 +1,5 @@
+class AddSpedToSurveyItemResponse < ActiveRecord::Migration[7.0]
+  def change
+    add_reference :survey_item_responses, :sped, foreign_key: true
+  end
+end