Fixed some APIs that worked mins ago....something strange happening with EF relationships.

API/Data/DataContext.cs

@@ -39,6 +39,11 @@ namespace API.Data
                 .WithOne(u => u.Role)
                 .HasForeignKey(ur => ur.RoleId)
                 .IsRequired();
+            // AppUsers have Libraries, not other way around
+            builder.Entity<Library>()
+                .HasMany(p => p.AppUsers)
+                .WithMany(p => p.Libraries)
+                .UsingEntity(j => j.ToTable("AppUserLibrary"));
         }
         
         void OnEntityTracked(object sender, EntityTrackedEventArgs e)