I have an ASP.NET Core 2.2 WEB API that has to have the ability to authenticate users with their Azure AD credentials. I have read a lot about this, but have no experience with it and maybe I just need to find the correct resources. Here's the overall situation:

The app is about school management. Each school will have it's own profile in the DB. When a school decides to use the product, they need to be able to allow their users to log into their school profiles using their email and password from their school's Azure Active Directory. Is it even possible to integrate AD authentication for different (multiple) organizations?

When they are prompted to enter their Microsoft credentials, how do I authenticate them against their specific AD? It's not just 'login via school A'. It's 'login via school A or school B or school C. etc.' that's giving me problems