Get available multi appointments.

Sample request:

{
    "AppointmentID": "",
    "BusinessID": "237677",
    "ServiceIDs": "16446543",
    "ServiceProviderIDs": "74635560",
    "AppointmentDate": "2020-05-06",
    "StyleID": null,
    "IsPublic": false,
    "IsOutcallAppointment": false,
    "CurrencySymbol": "$",
    "IsFromWidgetPage": 0,
    "IsFromShopAdmin": true,
    "IsMoveBack": false,
    "BusinessPackageID": "0",
    "PromotionID": 0
}