Task break down for WebSub implementation

[shafreenAnfar]

Design #786

Task Breakdown

• [x] Create a new repository for websubhub
• [x] Complete the subscriber listener in websub
• [x] Complete the HubListener and HubStartupService and HubService
• [x] Complete the publisher-client in websubhub
• [x] Send acknowledgment automatically if not specified in onSubscriptionValidationDenied
• [x] Auto generate a dynamic path segment if no path is given during service declaration
• [x] Returned Hub errors should be able to send user specified headers and payload
• [x] Subscription request with additional parameters should be able to access in Hub
• [x] Test with subscription URL with query paprams
• [x] Print a warning if it is not running on HTTPS
• [x] Add BBE for subscriber service
• [x] Complier plugin for service validation

Post GA

• [ ] Complete the subscriber-client in websub
• [ ] Multipart publisher update message support
• [ ] Complete the default implementation of InMemoryWebsubHub
• [ ] Lease seconds expired event
• [ ] Re-Subscription event

[niveathika]

@shafreenAnfar As per the design, shouldn't the publisher-client be in websubhub

[shafreenAnfar]

Yeah, you are right. Let me fix it.