chore: one off SMS campaign APIs (#2589)

db/migrate/20210707142801_add_campaign_type_to_campaigns.rb

@@ -0,0 +1,10 @@
+class AddCampaignTypeToCampaigns < ActiveRecord::Migration[6.0]
+  def change
+    change_table :campaigns, bulk: true do |t|
+      t.integer :campaign_type, default: 0, null: false, index: true
+      t.integer :campaign_status, default: 0, null: false, index: true
+      t.jsonb :audience, default: []
+      t.datetime :scheduled_at, index: true
+    end
+  end
+end