gistfile1.cs

public class User : IPerson, ICredential
{ ... }
public class UserConfiguration : EntityTypeConfiguration
{
    // Add already made configurations for IPerson and ICredential
    ConfigureAnyType(this, typeof(User));
}
public static void ConfigureAnyType(EntityTypeConfiguration<Type> entity, Type modelType)
{
    delegate configureDelegates;
    // Don't have the LINQ correct here..
    // Basically want to add the delegate for each interface 'entity' inherits from
    configureDelegates += configDelegateDict.Any(t => t.Value).Where(u => u.Key == type);
}