Hi @guido,
From a general perspective, Contentful is optimized for content creation, instead of specifically providing authentication to multiple users outside of a given organization.
That means that you’d have to implement most of the user-related components, such as registration, password recovery, authorization, or integrate another third-party service with our API.
With that, you’d integrate this with our Management API to perform content modifications from these users (e.g. upload, save content, etc). And, as always, these would also have to be bounded by our existing API rate limits (there’s an API rate limit of 10 requests per second for the Content Management API).
Let me know if that makes sense or if you have any other questions =)