We have a legacy D365 CE custom portal using B2C for authentication. The platform associated with this portal is coming towards the end of its life and we are planning to move services from it to our new platform, which is also D365 CE and which doesn't currently have an associated portal.
As we are running both in parallel, we are synchronising contacts between the two production environments.
We wish to create a Customer Service portal in the new environment to allow creation of new services in the new platform, while continuing to run the old platform and portal so that customers can access existing services there until we are able to migrate them.
I have two questions:
1) assuming we ensure sync of the External IDs associated with contact records in the old environment, are there any issues with continuing to use our existing B2C for sign up/sign in to the new portal?
2) what is the best way of ensuring that customers can seamlessly see all of their previous cases (whether on the old environment or the new one) no matter which portal they actually log into?
I appreciate that the most sensible answer may be "don't do it like this". Sadly this is unlikely to be an option.