docs(storage): add samples

[HemangChothani]

Add samples:

1. storage_bucket_delete_default_kms_key

2. storage_compose_file

3. storage_create_bucket_class_location

4. storage_define_bucket_website_configuration

5. storage_download_public_file

6. storage_get_service_account

7. storage_object_csek_to_cmek

8. storage_object_get_kms_key

9. storage_set_bucket_public_iam

[kurtisvg]

Please use a UUID for bucket names to ensure they don't conflict when running multiple times

[kurtisvg]

Please use a fixture to delete these bucket, so it's always done even if the test fails or encounters another error. You can use a generator to return a UUID above clean up after the bucket it created.

[kurtisvg]

Doesn't look like this tests anything

Suggested change

assert test_bucket.default_kms_key_name is None

[kurtisvg]

Does this actually verify this sample works? Won't this just ready an empty file if not?

The preferred pattern for samples is Arrange, Act, Assert:

1. Arrange - prepare the request
2. Act - send request, and receive response
3. Assert - Print response (to show the user how to interact with it) and assert the response occurred when the sample was run

It's an explict non-goal for our samples tests to test the service or product. Instead they should be that the sample ran successfully, and should verify the output of the sample in a reasonable way. Thus, most sample tests should be in the pattern:

1. Run the sample
2. Check the output of the sample

[kurtisvg]

nit: You can also use black to auto format these files

Suggested change

	bucket = storage_define_bucket_website_configuration.\
	define_bucket_website_configuration(test_bucket.name, "index.html", "404.html")
	bucket = storage_define_bucket_website_configuration.define_bucket_website_configuration(
	test_bucket.name, "index.html", "404.html")

[kurtisvg]

Suggested change

	# Copyright 2020 Google Inc. All Rights Reserved.
	# Copyright 2020 Google LLC. All Rights Reserved.

Please adjust everywhere.

[HemangChothani]

@frankyn Could you please review this PR, I am unable to add you as a reviewer.

[frankyn]

@JesseLovelace is on point for these reviews. Assigning it to them!

[busunkim96]

@HemangChothani Could you investigate the failing test? Do we need to add a new resource to the project?

================================== FAILURES ===================================
___________________________ test_object_csek_to_cmek ___________________________
Traceback (most recent call last):
  File "/tmpfs/src/github/python-docs-samples/storage/cloud-client/encryption_test.py", line 122, in test_object_csek_to_cmek
    BUCKET, test_blob_name, TEST_ENCRYPTION_KEY, KMS_KEY
  File "/tmpfs/src/github/python-docs-samples/storage/cloud-client/storage_object_csek_to_cmek.py", line 40, in object_csek_to_cmek
    token, rewritten, total = dest.rewrite(source_blob)
  File "/tmpfs/src/github/python-docs-samples/storage/cloud-client/.nox/py-3-6/lib/python3.6/site-packages/google/cloud/storage/blob.py", line 2098, in rewrite
    timeout=timeout,
  File "/tmpfs/src/github/python-docs-samples/storage/cloud-client/.nox/py-3-6/lib/python3.6/site-packages/google/cloud/_http.py", line 423, in api_request
    raise exceptions.from_http_response(response)
google.api_core.exceptions.BadRequest: 400 POST https://storage.googleapis.com/storage/v1/b/python-docs-samples-tests/o/test_blob_2eed0931e61a435a98f112685f291785/rewriteTo/b/python-docs-samples-tests/o/test_blob_2eed0931e61a435a98f112685f291785?destinationKmsKeyName=projects%2Fpython-docs-samples-tests%2Flocations%2Fus%2FkeyRings%2Fgcs-kms-key-ring%2FcryptoKeys%2Fgcs-kms-key: The provided encryption key is incorrect.
--------------------------- Captured stdout teardown ---------------------------
Ignoring 404, detail: 404 DELETE https://storage.googleapis.com/storage/v1/b/python-docs-samples-tests/o/test_blob_2eed0931e61a435a98f112685f291785?generation=1589490963804584: No such object: python-docs-samples-tests/test_blob_2eed0931e61a435a98f112685f291785

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