As a platform engineer, I want the gateway to parse the MCP request body, extract the method and tool name, set the corresponding MCP session ID in headers for upstream mcp server, and rewrite tool names as needed to hide internal prefixes.

Considerations:

• Handle JSON-RPC body parsing in ext-proc safely (validate schema, avoid panics)
• Extract from body & put into headers:
  • method (e.g. initialize, tools/call )
  • params.name (e.g. tool name)
• Replace mcp-session-id in headers based on corresponding mcp-server upstream
• Include tracing or debug logs for filtered requests
• Support tool name rewriting rules (e.g. prefix stripping)