Details about the record. For example: Name = "Mark", Description = "Description", ID = "263rd72c-edfc-4dc5-b72f-45104fe5ef43", externalId = "4614d72c-edfd-4dc5-b72f-45104fe5ef43".

Note: The fields/properties must be part of the schema/metadata created for the custom object (in this case, Name, Description, ID. and externalId must be fields in the schema). The schema and metadata can be generated using the Schema Manager API.

Refer to the following table to understand the behavior when you want to upsert records by ID field.

         | ID in payload? | ExternalId in payload? | Behavior | Validation |
         |----------------|------------------------|----------|------------|
         | Yes            | Yes                    | Update the record using the `ID` if it exists, and ensure that the `externalId` is unique. | ExternalId unique validation |
         | Yes            | No                     | Update the record using the `ID` if it exists, and ensure that the `externalId` is unique. | NA |
         | No             | Yes                    | Generate a new GUID to use as the ID, create a new record with ID, and ensure the `externalId` is unique. | ExternalId unique validation |
         | No             | No                     | Generate a new GUID to use as the ID, create a new record with ID, and ensure the `externalId` remains null. | NA |
         Refer to the following table to understand the behavior when you want to upsert records by externalId field.
        
         | ID in payload? | ExternalId in payload? | Behavior | Validation |
         |----------------|------------------------|----------|------------|
         | Yes            | Yes                    | Update the record using the `externalId` if it exists. | The record's ID must match the ID provided in the payload. If not, give an error. Do not allow the ID to be updated in any case. |
         | Yes            | No                     | Update the record using the `ID` if it exists, keeping `externalId` unchanged. If the `ID` does not exist, create a new record with that ID, and set the `externalId` to null. | NA |
         | No             | Yes                    | Update the record using the `externalId` if it exists. | NA |
         | No             | No                     | Generate a new GUID to use as the ID, create a new record with ID, and ensure the `externalId` remains null. | NA |