chore: one off SMS campaign APIs (#2589)

spec/controllers/api/v1/accounts/campaigns_controller_spec.rb

@@ -106,6 +106,28 @@ RSpec.describe 'Campaigns API', type: :request do
         expect(response).to have_http_status(:success)
         expect(JSON.parse(response.body, symbolize_names: true)[:title]).to eq('test')
       end
+
+      it 'creates a new oneoff campaign' do
+        twilio_sms = create(:channel_twilio_sms, account: account)
+        twilio_inbox = create(:inbox, channel: twilio_sms)
+        label1 = create(:label, account: account)
+        label2 = create(:label, account: account)
+
+        post "/api/v1/accounts/#{account.id}/campaigns",
+             params: {
+               inbox_id: twilio_inbox.id, title: 'test', message: 'test message',
+               scheduled_at: 2.days.from_now,
+               audience: [{ type: 'Label', id: label1.id }, { type: 'Label', id: label2.id }]
+             },
+             headers: administrator.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:success)
+        response_data = JSON.parse(response.body, symbolize_names: true)
+        expect(response_data[:campaign_type]).to eq('one_off')
+        expect(response_data[:scheduled_at].present?).to eq true
+        expect(response_data[:audience].pluck(:id)).to include(label1.id, label2.id)
+      end
     end
   end