Add support for notification trigger management and poll notifications

[const-cloudinary]

Adds trigger management and the poll notification transport to the Python SDK. Poll notifications let a client receive notifications without exposing a public webhook endpoint: notifications are buffered server-side against a poll:// trigger and drained over long-poll.

Admin API

Trigger management: triggers, create_trigger, update_trigger, delete_trigger, test_trigger.

Poll transport: notifications and ack_notifications, addressed by either a named channel or a batch_id. notifications raises ValueError unless exactly one of the two is given, mirroring the server.

Signature verification

utils.verify_notification(message) verifies a polled message envelope directly:

for msg in api.notifications(channel="orders", wait_seconds=20).get("messages", []):
    if utils.verify_notification(msg):
        handle(msg["payload"])

It decodes signed_payload and verifies against those bytes, then delegates to the existing verify_notification_signature. This matters because signatures cover the byte-exact signed payload: verifying against a re-serialization of the parsed payload, or against the undecoded base64, returns a silent False that reads as a forged notification. utils.base64url_decode is exposed for callers who need the raw bytes.

Also fixes a TypeError in verify_notification_signature when timestamp is a string — the form both the poll envelope and the X-Cld-Timestamp header actually deliver, so the comparison raised on every real message.

Other changes

• batch_id on upload, archive, multi, sprite and bulk delete parameters (signed automatically)
• request_id on Admin API responses (Response.request_id attribute) and Upload API results (request_id key). The Upload API return type stays a plain dict
• Module-first URLs in the v2 API client (/v2/{module}/{cloud_name}/...), which the notifications endpoints require
• cloudinary.config(timeout=...) now honored on Admin API calls; a per-call timeout still wins
• HTTP 503 mapped to GeneralError

Testing

Mocked coverage for triggers, notifications, verification and request_id propagation, plus two live end-to-end tests: a trigger create/list/update/delete lifecycle, and an upload that is polled, signature-verified and acknowledged against the real API. Both clean up after themselves and skip without credentials.

Verified against a live product environment: 178 passed.