Actions on google reservations for transaction API

Question

We are building boot using action on builder SDK. In bot we have transaction related feature so we want to implement reservation feature to make appointment reservation. In our Bot we just need reservation. user can't cancel/delete reservation (As our member can contact the user for next 3 4 days, we are just asking user free time so we can contact user). (We did't have reservation feature yet but google team force us to do so). My Question is while implementing reservation we have https://developers.google.com/assistant/transactions/physical/dev-guide-physical-reservations#validate_transaction_requirements_optional this feature optional we are not implementing this, for second step we have to build Order like this https://developers.google.com/assistant/transactions/physical/dev-guide-physical-reservations#build_the_order

 const order = {
   createTime: '2019-09-24T18:00:00.877Z',
   lastUpdateTime: '2019-09-24T18:00:00.877Z',
   merchantOrderId: orderId, // A unique ID String for the order
   userVisibleOrderId: orderId,
   transactionMerchant: {
     id: 'http://www.example.com',
     name: 'Example Merchant',
   },
   contents: {
     lineItems: [
       {
         id: 'LINE_ITEM_ID',
         name: 'Dinner reservation',
         description: 'A world of flavors all in one destination.',
         reservation: {
           status: 'PENDING',
           userVisibleStatusLabel: 'Reservation is pending.',
           type: 'RESTAURANT',
           reservationTime: {
             timeIso8601: '2020-01-16T01:30:15.01Z',
           },
           userAcceptableTimeRange: {
             timeIso8601: '2020-01-15/2020-01-17',
           },
           partySize: 6,
           staffFacilitators: [
             {
               name: 'John Smith',
             },
           ],
           location: {
             zipCode: '94086',
             city: 'Sunnyvale',
             postalAddress: {
               regionCode: 'US',
               postalCode: '94086',
               administrativeArea: 'CA',
               locality: 'Sunnyvale',
               addressLines: [
                 '222, Some other Street',
               ],
             },
           },
         },
       },
     ],
   },
   buyerInfo: {
     email: '[email protected]',
     firstName: 'Jane',
     lastName: 'Doe',
     displayName: 'Jane Doe',
   },
   followUpActions: [
     {
       type: 'VIEW_DETAILS',
       title: 'View details',
       openUrlAction: {
         url: 'http://example.com',
       },
     },
     {
       type: 'CALL',
       title: 'Call us',
       openUrlAction: {
         url: 'tel:+16501112222',
       },
     },
     {
       type: 'EMAIL',
       title: 'Email us',
       openUrlAction: {
         url: 'mailto:[email protected]',
       },
     },
   ],
   termsOfServiceUrl: 'http://www.example.com'
 };

According to doc we have to create order object like above, but we are unable to find any doc what are optional filed in above object and what value to pass for reservationTime and userAcceptableTimeRange.

reservationTime: {
         timeIso8601: '2020-01-16T01:30:15.01Z',
       },
       userAcceptableTimeRange: {
         timeIso8601: '2020-01-15/2020-01-17',
       }

Further more do we need to implement Set up asynchronous requests to the Orders API (https://developers.google.com/assistant/transactions/physical/dev-guide-physical-reservations#set_up_asynchronous_requests_to_the_orders_api) as we don't need to update user appoint time and user can't cancel appointment.

Is there any other way we can avoid reservation? please guide me, thanks in advance.