We would like to initiate a journey for 'new' users via the Rest API (POST /interaction/v1/events, see documentation). These users are new in SFMC. In other words, we have no contact (email address and associated subscriber key) in SFMC for such users.
We have some ideas to do that: We generate a unique subscriber key in our (client) application and after that we call the API with the new subscriber key ("ContactKey"), while the email-address is placed in the "Data" attribute field. That means, the journey has to install the new contact in SFMC, so we can send an email to such user.
So, our questions are: Is it in general possible to initiate a journey for "unknow" SFMC users? How can we install a new contact (subscriber key) in SFMC inside a journey? Or can you advise us another approach? Remark: We like to use a journey and it has to be just one API call, in order to reduce complexity on our side.