I need to authenticate users from an existing legacy Users Table, but I would like to do it on the shoulders of Identity and Authorization, if possible, so that the features and attributes are at my disposal. Most of our users already have logins from a much older native application that we want to carry over to our Asp.net Core Intranet Web App. I've seen a few topics on this issue on SO and other places, but none seem to suit my specific needs.
What is the best way I should go about this?