fix: Add missing product region tags for Cloud CDN snippets (GoogleCl…

…oudPlatform#9258)

## Description

Cloud CDN Snippets are missing product's specific region tags. In this PR, we are only adding region tags. No code changes. For more details, refer to [b/264905390](b/264905390).

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

## Checklist
- [ ] I have followed [Sample Guidelines from AUTHORING_GUIDE.MD](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md)
- [ ] README is updated to include [all relevant information](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md#readme-file)
- [ ] **Tests** pass:   `nox -s py-3.9` (see [Test Environment Setup](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] **Lint** pass:   `nox -s lint` (see [Test Environment Setup](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] These samples need a new **API enabled** in testing projects to pass (let us know which ones)
- [ ] These samples need a new/updated **env vars** in testing projects set to pass (let us know which ones)
- [x] Please **merge** this PR for me once it is approved.
- [ ] This sample adds a new sample directory, and I updated the [CODEOWNERS file](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/.github/CODEOWNERS) with the codeowners for this sample

cdn/snippets.py

@@ -31,6 +31,7 @@
 
 
 # [START sign_url]
+# [START cloudcdn_sign_url]
 def sign_url(url, key_name, base64_key, expiration_time):
     """Gets the Signed URL string for the specified URL and configuration.
 
@@ -68,8 +69,10 @@ def sign_url(url, key_name, base64_key, expiration_time):
             url=url_to_sign, signature=signature)
 
     print(signed_url)
+# [END cloudcdn_sign_url]
 
 
+# [START cloudcdn_sign_url_prefix]
 def sign_url_prefix(url, url_prefix, key_name, base64_key, expiration_time):
     """Gets the Signed URL string for the specified URL prefix and configuration.
 
@@ -111,10 +114,12 @@ def sign_url_prefix(url, url_prefix, key_name, base64_key, expiration_time):
             signature=signature)
 
     print(signed_url)
+# [END cloudcdn_sign_url_prefix]
 # [END sign_url]
 
 
 # [START cdn_sign_cookie]
+# [START cloudcdn_sign_cookie]
 def sign_cookie(url_prefix, key_name, base64_key, expiration_time):
     """Gets the Signed cookie value for the specified URL prefix and configuration.
 
@@ -147,6 +152,7 @@ def sign_cookie(url_prefix, key_name, base64_key, expiration_time):
             policy=policy, signature=signature)
     print(signed_policy)
 # [END cdn_sign_cookie]
+# [END cloudcdn_sign_cookie]
 
 
 if __name__ == '__main__':