After configuration AD FS I tried to connect to the endpoint "......adfs/services/trust/13/usernamemixed" and to the endpoint "...../services/trust/13/windowsmixed". But I got the error "HTTP Error 503. The service is unavailable.".
The endpoints was enabled in the AD FS management.
The problem was in port. The matter is the usual port for AD FS was busy. To fix the problem you need:
Now try to open on browser some endpoint. You will be able to see:
It means all works correctly and you can use endpoints programmatically.
The good article about customization the AD FS login flow in OWA.