feat(storage): support delete_source_objects in compose API (Address PR feedback)

[nidhiii-27]

This update addresses the PR comments by:

• Improving the system test cleanup logic and removing unnecessary fixture dependencies for the specific test case.
• Enhancing the unit test to verify that destination properties (like contentType) are correctly passed in the request body during a compose operation.
• Re-verifying all unit and system tests pass.

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PR created automatically by Jules for task 5220279067164674388 started by @nidhiii-27

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[gemini-code-assist]

Code Review

This pull request introduces a delete_source_objects parameter to the Blob.compose method, allowing source blobs to be automatically deleted after a successful composition. The changes include updates to the method signature, docstrings, and request logic, along with new unit and system tests. Feedback was provided to improve the robustness of the system test by using the blobs_to_delete fixture for resource cleanup instead of a manual try...finally block, which helps prevent resource leaks and avoids masking potential errors.

[gemini-code-assist]

The manual try...finally block for cleanup is less robust than using the blobs_to_delete fixture. If destination.compose fails before the object is created, destination.delete() in the finally block will raise a NotFound exception, which can mask the original error. Furthermore, if the test fails during the upload or composition steps, the source blobs will be leaked. Using the standard blobs_to_delete fixture ensures all resources are cleaned up safely even on failure and simplifies the test logic.

Suggested change

	def test_blob_compose_delete_source_objects(shared_bucket):
	payload_1 = b"AAA\n"
	source_1 = shared_bucket.blob("source-1-delete")
	source_1.upload_from_string(payload_1)
	payload_2 = b"BBB\n"
	source_2 = shared_bucket.blob("source-2-delete")
	source_2.upload_from_string(payload_2)
	destination = shared_bucket.blob("destination-delete")
	destination.compose([source_1, source_2], delete_source_objects=True)
	try:
	assert destination.download_as_bytes() == payload_1 + payload_2
	assert not source_1.exists()
	assert not source_2.exists()
	finally:
	destination.delete()
	def test_blob_compose_delete_source_objects(shared_bucket, blobs_to_delete):
	payload_1 = b"AAA\n"
	source_1 = shared_bucket.blob("source-1-delete")
	source_1.upload_from_string(payload_1)
	blobs_to_delete.append(source_1)
	payload_2 = b"BBB\n"
	source_2 = shared_bucket.blob("source-2-delete")
	source_2.upload_from_string(payload_2)
	blobs_to_delete.append(source_2)
	destination = shared_bucket.blob("destination-delete")
	blobs_to_delete.append(destination)
	destination.compose([source_1, source_2], delete_source_objects=True)
	assert destination.download_as_bytes() == payload_1 + payload_2
	assert not source_1.exists()
	assert not source_2.exists()