fix: fixed an error when rolling back a transaction that did not execute begin

[halnique]

Fix: #165

Several features and tests were broken due to the google/cloud-spanner v1.68.0 release.

• An exception is thrown if rollback is performed without any query call in the transaction.
• Tests that depend on the query execution order called from the cursor() method fail.

Checklist

• CHANGELOG

Reference

• https://github.com/googleapis/google-cloud-php-spanner/releases/tag/v1.68.0

[halnique]

The processing order of the cursor() method of the Result class has changed.
Before the change, a generator was generated and validated when the rows() method was called, but after the change, a generator is generated and validated when the Result class is initialized.
In other words, the timing at which the query specified in the cursor() method is executed has changed from when the Generator::current() method is called to when the Connection::cursor() method is called.

ref: https://github.com/googleapis/google-cloud-php/pull/6708/files#diff-1c94ccf8ee4a0849e0cd857c1fb93ea32906963063a3652d9e3263412cb9267e

Before the change, the test code would fail due to this effect.

1) Colopl\Spanner\Tests\SessionNotFoundTest::test_session_not_found_on_cursor
Transaction should be called twice
Failed asserting that 3 matches expected 2.

/project/tests/SessionNotFoundTest.php:174

The reason why $passes is 3 is because it is handled as follows.

1.$cursor = $conn->cursor('SELECT 12345'); succeeds and executeStreamingSql is sent
2.$this->deleteSession($conn); is called
3.$passes++; value is 1
4.$this->assertEquals([12345], $cursor->current()); succeeds but is not expected
5.$passes++; value is 2
6. attempts to commit the transaction but fails because the session has been deleted and tries to retry handling NotFoundException
7. $cursor = $conn->cursor('SELECT 12345'); succeeds and executeStreamingSql is sent
8. $this->assertEquals([12345], $cursor->current()); succeeds
9. $passes++; value is 3
10. commit the transaction

[halnique]

When rolling back a transaction, an exception is now thrown if the target transactionId is not specified.

ref: https://github.com/googleapis/google-cloud-php/pull/6708/files#diff-25ee9adab31aa54b734a2bc5f254b0e922b13e1c0ad27f1fff60a9a534552a03
L192-L194

This caused the following tests to fail.

1) Colopl\Spanner\Tests\ConnectionTest::test_connection_transaction_reset_on_exceptions
InvalidArgumentException: Rollback failed: Transaction not initiated.

/project/vendor/google/cloud-spanner/src/Operation.php:193
/project/vendor/google/cloud-spanner/src/Transaction.php:572
/project/src/Concerns/ManagesTransactions.php:172
/project/vendor/laravel/framework/src/Illuminate/Database/Concerns/ManagesTransactions.php:264
/project/src/Concerns/ManagesTransactions.php:73
/project/vendor/google/cloud-spanner/src/Database.php:957
/project/vendor/google/cloud-core/src/Retry.php:80
/project/vendor/google/cloud-spanner/src/Database.php:975
/project/src/Concerns/ManagesTransactions.php:76
/project/src/Connection.php:525
/project/src/Concerns/ManagesTransactions.php:81
/project/tests/ConnectionTest.php:541

Originally, when a transaction was called without specifying any options, Operation::beginTransaction() was called internally to set the transactionId.
With this change, the default options specified have been changed and Operation::beginTransaction() is no longer called internally.

ref: https://github.com/googleapis/google-cloud-php/pull/6708/files#diff-25ee9adab31aa54b734a2bc5f254b0e922b13e1c0ad27f1fff60a9a534552a03
L495-L497

As a result, InvalidArgumentException('Rollback failed: Transaction not initiated.') exception is thrown when rollback is done without calling any query in Database::runTransaction().