Automating redemption of invitations

Hello Clemence - thanks for your question!

I think you are asking for a stand alone portal that can perhaps perform self-service sign-up.

This is possible with our APIs as described in the documentation here: https://docs.microsoft.com/en-us/azure/active-directory/active-directory-b2b-api

We are in the process of publishing code samples on Github that will show you one way to do this.

Here it is: https://github.com/Azure/active-directory-dotnet-graphapi-b2bportal-web 

Please note - treat this as "Alpha" level code. We are still working on it and making updates.