Reference to the Database, provided by rorm_db_connect.
callback function. Takes the context, a pointer to a transaction and an Error.
Pass through void pointer.
**Important**: Rust does not manage the memory of the transaction. To properly free it, use rorm_transaction_free, rorm_transaction_commit or rorm_transaction_abort.
This function is called from an asynchronous context.
Starts a transaction on the current database connection.