Rollback non-relational database transactions.

Also, added comment to clarify it.

framework/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Uow/EntityFrameworkCore/EfCoreTransactionApi.cs

@@ -48,11 +48,19 @@ namespace Volo.Abp.Uow.EntityFrameworkCore
             DbContextTransaction.Dispose();
         }
 
-        public Task RollbackAsync(CancellationToken cancellationToken)
+        public async Task RollbackAsync(CancellationToken cancellationToken)
         {
-            return DbContextTransaction.RollbackAsync(
-                CancellationTokenProvider.FallbackToProvider(cancellationToken)
-            );
+            await DbContextTransaction.RollbackAsync(CancellationTokenProvider.FallbackToProvider(cancellationToken));
+
+            foreach (var dbContext in AttendedDbContexts)
+            {
+                if (dbContext.As<DbContext>().HasRelationalTransactionManager())
+                {
+                    continue; //Relational databases use the shared transaction
+                }
+
+                await dbContext.Database.RollbackTransactionAsync(CancellationTokenProvider.Token);
+            }
         }
     }
 }

framework/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Uow/EntityFrameworkCore/UnitOfWorkDbContextProvider.cs

@@ -191,7 +191,10 @@ namespace Volo.Abp.Uow.EntityFrameworkCore
                 }
                 else
                 {
-                    dbContext.Database.BeginTransaction(); //TODO: Why not using the new created transaction?
+                    /* No need to store the returning IDbContextTransaction for non-relational databases
+                     * since EfCoreTransactionApi will handle the commit/rollback over the DbContext instance.
+                     */
+                    dbContext.Database.BeginTransaction();
                 }
 
                 activeTransaction.AttendedDbContexts.Add(dbContext);
@@ -236,7 +239,10 @@ namespace Volo.Abp.Uow.EntityFrameworkCore
                 }
                 else
                 {
-                    await dbContext.Database.BeginTransactionAsync(GetCancellationToken()); //TODO: Why not using the new created transaction?
+                    /* No need to store the returning IDbContextTransaction for non-relational databases
+                     * since EfCoreTransactionApi will handle the commit/rollback over the DbContext instance.
+                     */
+                    await dbContext.Database.BeginTransactionAsync(GetCancellationToken());
                 }
 
                 activeTransaction.AttendedDbContexts.Add(dbContext);