Server-Sent Events (SSE) support added for real-time streaming

FastAPI 0.135.0 introduces native Server-Sent Events (SSE) support, enabling efficient one-way real-time data streaming from server to clients. This provides an alternative to WebSockets for scenarios requiring only server-to-client push.

For endpoints needing real-time updates to clients, evaluate SSE as a simpler alternative to WebSockets. Monitor connection duration metrics and open connection counts for SSE endpoints, as they maintain persistent HTTP connections. Ensure load balancers and proxies support long-lived HTTP connections.