Creating a staged user with an API call

I would try creating a topic via incoming email:

This way a staged user will be created on topic creation.

You could create the staged user via the api

curl -i -sS -X POST "http://localhost:4200/users"  \
-H "Content-Type: multipart/form-data"  \
-H "Api-Key: 3e8aa0b7970cf010da24d06215fdc7b3951352c61a59ada70f5f36b4ce890bb2"  \
-H "Api-Username: system"  \
-F "name=2e6ac3603"  \
-F "active=false"  \
-F "staged=true"  \
-F "username=2e6ac3603"  \
-F "email=2e6ac3603@example.com"  \
-F "password=f9b4c3c7ebd1c2877a0ad659be6ca83e"

and then create the topic for the user but, on the user create action discourse will then send an activation email:

{“success”: true,“active”: false,“message”: “You’re almost done! We sent an activation mail to 2e6ac3603@example.com. Please follow the instructions in the mail to activate your account.If it doesn’t arrive, check your spam folder.”}