[BsonKnownTypes(typeof(TopSection), typeof(FooterSection))]
public record Section(string Type);

[BsonDiscriminator("TopSection")]
public record TopSection(string Type, string Title, string Description) : Section(Type);

[BsonDiscriminator("FooterSection")]
public record FooterSection(string Type, string Title, string Link) : Section(Type);

[BsonDiscriminator("MiddleSection")]
public record MiddleSection(string Type, string Title, int Views) : Section(Type);

public record Page : IViewModel
{
    [BsonId]
    public string Id { get; init; }    
public string Language { get; init; }    
public IEnumerable<Section> Sections { get; init; } = [];
}

public interface IReadonlyPageRepository : IReadonlyRepository<Page> { }
public class Repository : ReadonlyRepository<Page>, IReadonlyPageRepository
{
    public Repository(IMongoStoreFactory factory) : base(factory, "sections")
    {
        BsonSerializer.RegisterDiscriminatorConvention(typeof(Section), new ScalarDiscriminatorConvention("type"));
    }
} 

try
{
    BsonSerializer.RegisterDiscriminatorConvention(typeof(Section), new ScalarDiscriminatorConvention("type"));
} catch
{
}