BulkUpsert can be used for inserting new contacts and updating existing contacts in the master_contact table.
This method takes a column list and a contactDatas array. All the data will be processed according to the columns list.
You can add/update 1000 record lines in a single call.
contact_key column in master_contact table is mandatory and unique across all the contacts.
So, for all items in the request body, the contact_key is mandatory parameter.
Apart from the predefined columns in master_contact table, the users are allowed to update their custom columns in this table, provided that the column name/value pair is compatible with the table structure.
This method should be called once a minute with a single request! Paralel calls can cause Internal Error 500