mcp: support custom notifications - #1146
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Protocol extensions can define custom JSON-RPC notifications, but the SDK only exposes helpers for standard notifications. Add SendNotification to client and server sessions. Route custom notifications through sending middleware and preserve arbitrary parameters. Fixes modelcontextprotocol#745.
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Protocol extensions need to send and receive custom JSON-RPC notifications. The SDK session APIs currently support only standard notification methods.
This change adds:
SendNotificationtoClientSessionandServerSession.AddReceivingCustomNotificationregistration for typed client handlers.SendSubscriptionNotificationfor custom notifications onsubscriptions/listenstreams.io.modelcontextprotocol/subscriptionIdmetadata on subscription notifications.Sending middleware processes custom notifications before transmission. Typed receiving handlers use parameter structs that embed
ParamsBase.The tests cover:
Validation:
This PR supersedes #844.
Fixes #745