public class TimeRecord
	...

	public required TimeRecordSource Source { get; set; }
}
public class TimeRecordSource
{
	public required TimeRecordSourceType Type { get; set; }
	public string? Name { get; set; }
	public string? Id { get; set; }
}
public enum TimeRecordSourceType
{
	Unknown = 0,
	Device,
	Operator,
}

public class TimeRecordConfiguration : IEntityTypeConfiguration<TimeRecord>
{
	public void Configure(EntityTypeBuilder<TimeRecord> builder)
	{
		...
		builder.OwnsOne(typeof(TimeRecordSource), nameof(TimeRecord.Source));
	}
}

builder.OwnsOne(typeof(TimeRecordSource), nameof(TimeRecord.Source)).Property(nameof(TimeRecordSource.Type)).HasConversion<string>().HasMaxLength(50);