Document the new savepoint API

[roji]

Following #20176

In the transactions page.

[Tommigun1980]

Please add the documentation as it's hard to test new features in the preview builds without any documentation whatsoever. Thanks!

[AliCharper]

@Tommigun1980

I did provide an example

  private static void ShouldbeRolledBackatSomeStages()
        {
            TaxDbContext _Context = new TaxDbContext();

            using (var transaction = _Context.Database.BeginTransaction())
            {
                var NewAssetComponent = new Asset_Component
                {
                    AcquisitionDate = DateTime.Now,
                    AssetId = Guid.NewGuid(),
                    Cost = 110,
                    Description = new Random().Next().ToString() + " New Component",
                    QualifyingAmount = 10000,
                };

                //
                _Context.Asset_Components.Add(NewAssetComponent);

                _Context.SaveChanges();

                _Context.Database.CreateSavepoint("First_SavePoint");

                var NewAsset_Details = new Asset_Details
                {
                    AssetId = Guid.NewGuid(),
                    Description = new Random().Next().ToString() + " New Desc",
                };

                _Context.Asset_Details.Add(NewAsset_Details);

                _Context.SaveChanges();

                _Context.Database.CreateSavepoint("Second_SavePoint");

                var NewAsset_Version = new Asset_Version
                {
                    Notes= new Random().Next().ToString() + " New Note",
                    PurchaseDate=DateTime.Now
                };

                
                _Context.Asset_Version.Add(NewAsset_Version);

                _Context.SaveChanges();

                _Context.Database.CreateSavepoint("Third_SavePoint");
                
                _Context.Database.RollbackToSavepoint("First_SavePoint");

                //Commeting the Transaction
                transaction.Commit();
            }

        }

[AliCharper]

@Tommigun1980

I can send you the working/full solution if you need it.

[Tommigun1980]

Thanks a lot @AliCharper, I appreciate it!