Using Azure AD to land users on their custom login page from within your app

Hi Alex_Simons 

Thanks for providing the information. I was looking for this information for a while now. We have integrated our Sharepoint 2016 on prem server with Azure AD so that azure AD acts as a provider for our on prem sharepoint site by following - https://docs.microsoft.com/en-gb/azure/active-directory/saas-apps/sharepoint-on-premises-tutorial

My scenario is similar to your 'What about multi-tenant apps?' in your post

Our Sharepoint site is exposed externally to the internet and we allow external users from multiple companies to login to our site by creating their user accounts in our AD which then sync to Azure AD

Everything is working fine as expected however the login experience is not the best for external users. The user enters our sharepoint site url - https://apps.contoso.com which redirects to https://login.microsoftonline.com/<Tenant Id>/wsfed?wa=wsignin1.... First they have to enter their username in the email format and click next. Then the login prompt comes up where they have to again enter the username and password.

I would like to build a login page where all users (external and internal) can enter their username and password on the same page rather than having to go through the above process. Can you please guide me with the information on how to achieve this or a better expereince for login for external.

Thanks,

Moreno