This is custom developed. If you want an API to import for your clients, we can provide that as well. That is already in place, we just have to give you a way to authenticate to this API.
The workflow will be something of this sort.
1. Get your client to upload file. You can store this file also as a temporary file on your container. Each container has a temporary directory with name /tmp.
2. Call the api with and specify the url of this file pointing to the container which you uploaded to. Note if you have multiple containers you will have to specify the container Id as well which you can retrieve from the environment variable process.env.NC_CONTAINER_ID
When the api becomes available there will be a step by step guide how to do this.