Support filtering tools depends on request data (http-headers, etc) #608

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Expected Behavior

There is no way to filter available tools in toolsListRequestHandler() and toolsCallRequestHandler()
I would like to filter tools to specific clients depending on some data in http-headers.

Current Behavior

There is no way to filter tools dynamically. The only way to do it - inherit McpAsyncServer, and use same package io.modelcontextprotocol.server - because McpServerFeatures.Async used in constructor is package-private. So maybe also make McpServerFeatures.Async public?

Context

I would like to implement authorization to be able to restrict tool calls to specific clients.