Re: [Proposal] Add `savepoint()` method to PDO

Hi Saki, Aside from a few concerns, I think your proposal is very sensible. I have long felt a disconnect that while we have beginTransaction(), commit(), and rollback() methods, there's no equivalent functionality for SAVEPOINT in PDO. It seems natural to support these commonly used transactional features as part of PDO's functionality. Having consistent support through PDO would be greatly appreciated from a user perspective, but I do have concerns regarding the variations in SQL. The following code is quoted from Laravel: https://github.com/laravel/framework/blob/v10.43.0/src/Illuminate/Database/Query/Grammars/Grammar.php#L1307-L1310 ```php return 'SAVEPOINT '.$name; ``` While most databases use SAVEPOINT [name], but: https://github.com/laravel/framework/blob/v10.43.0/src/Illuminate/Database/Query/Grammars/SqlServerGrammar.php#L453-L456 ```php return 'SAVE TRANSACTION '.$name; ``` SQL Server uniquely uses SAVE TRANSACTION [name]. There might be other variations in databases, so full support could be challenging, which is something to be mindful of. > change the signature of rollback() to > rollback(?string $name = null). This might lead to confusion due to rollback() having multiple functionalities, as ROLLBACK and ROLLBACK TO [name] target different rollback operations. Just as beginTransaction() and savepoint() are separate, perhaps having a separate method for rolling back to a savepoint might maintain consistency, for example rollbackToSavepoint(string $name). Regards. Kentaro