This plugin adds WebSub (formerly PubSubHubbub) publisher and subscriber functionality to content management systems. It is designed for site owners and developers who want to enable real-time syndication of their content feeds, ensuring subscribers receive updates without manual polling.

• Publisher Notifications: Automatically sends notifications to configured WebSub hubs whenever a post is published or updated, triggering instant distribution to all subscribers.
• Multi-Feed Support: Works with all standard feed formats generated by the platform, including Atom, RSS2, and RDF, ensuring broad compatibility.
• Hub Discovery & Management: Adds the necessary link tags to feeds for hub discovery and allows administrators to specify custom hub endpoints for notifications.
• Subscriber API: Provides a REST API endpoint and a set of hooks that allow other plugins to act as subscribers, receiving and verifying updates from external WebSub-enabled feeds.
• Security & Verification: Includes support for HMAC signature verification using multiple algorithms (SHA1, SHA256, etc.) to ensure the integrity of delivered content from hubs.