Update 2. Build out BackEnd and Refactor.md

Author: davidfowl

docs/2. Build out BackEnd and Refactor.md

@@ -389,9 +389,9 @@ Okay, now we need to update our `ApplicationDbContext` so Entity Framework knows
                modelBuilder.Entity<ConferenceAttendee>()
                    .HasKey(ca => new { ca.ConferenceID, ca.AttendeeID });
 
-               // Many-to-many: Speaker <-> Session
-               modelBuilder.Entity<SessionSpeaker>()
-                   .HasKey(ss => new { ss.SessionId, ss.SpeakerId});
+               // Many-to-many: Session <-> Attendee
+               modelBuilder.Entity<SessionAttendee>()
+                   .HasKey(ca => new { ca.SessionID, ca.AttendeeID });
 
                // Many-to-many: Speaker <-> Session
                modelBuilder.Entity<SessionSpeaker>()