put https://{region}-api.dotdigital.com/contacts/v3/import
Imports a collection of contacts. Creates contacts if they do not exist and updates contacts if they do. This is an async operation and you will need to check when it is complete by calling getImportStatus
Note: It isn't possible to specify the value for the contactId field when creating a contact, so it is only used to check for a matching contact when specified
You can import a maximum of 50MB of data per call
Your JSON request body can be a maximum size of 50MB, therefore allowing a large number of contacts to be imported in a single call.