Creates a new user invitation and sends an email to the user with the instructions to create a new account.
imeis parameter allows specifying the devices that the user is allowed to access.
If this list is empty, user will have full access to the account's devices.
If boundary access is granted, user will have access to all boundaries in the account.
If no boundary access is specified, it defaults to true.
If accessDate is not specified, user will have access to the account starting in the current date.