OSPP_PR1:Add request-scoped context support for the Agent Gateway plugin - #7133

Background

Add request-scoped context support through a new Agent Gateway plugin without changing the existing AI Proxy or MCP implementation. The plugin provides an immutable request context that can be propagated through the Reactor chain and optionally returned as a response request ID.

Changes

• Add the shenyu-plugin-agent-gateway plugin and Spring Boot starter;
• Register plugin metadata and database initialization entries;
• Support strict rule-handle validation, Reactor context propagation, request isolation, response correlation, and cache cleanup;
• Keep the existing AI Proxy and MCP plugins reusable and independently configurable.

Verification

• Local JDK 17 verify: 13 reactor modules passed;
• RAT: Unapproved: 0, Unknown: 0, Generated: 0;
• RISC-V container simulation with Java 17 and Maven: 13 reactor modules passed;
• Admin → WebSocket → Gateway configuration synchronization passed;
• AI Proxy JSON, SSE, cancellation, and MCP coexistence were manually verified.

Scope

• Full MCP JSON-RPC tool workflow is not included;
• Native RISC-V hardware and GitHub CI have not been run;
• Other database dialects have not been executed;
• The upcoming mentor version has not yet been merged.