…ls (#437)

I noticed that #569 was merged (thanks!) and looked at the diff again
with fresh eyes and noticed that I reused the existing mutex for tool
middlewares within the resource middlewares. This means that, at least
while processing middlewares, it's possible a resource call could be
blocked waiting on a lock because of a tool call or vice-versa.

Since there's a separate mutex for tools, resources, etc, it seems
there's a desire to not block each other. This commit renames the
existing middleware mutex to better clarify it's specifically for tool
middlewares, and adds a new mutex for use specifically with resource
middlewares.

Signed-off-by: TJ Hoplock <[email protected]>

* feat!: add context.Context to TokenStore methods

In distributed environments a TokenStore will be implemented as a
database, and often a context is required when running get/store
operations to ensure cancellation propagation, instrumentation,
etc works when running token store ops. This is a breaking change
but I think it makes sense (and it's pretty easy to fix
any breakages).

* Add checks for context cancellation; add tests

* Document TokenStore requirements and add ErrNoToken sentinel error

* Detect Pong from MCP Client and skip Session ID validation.
https://modelcontextprotocol.io/specification/2025-03-26/basic/utilities/ping

* Use isJSONEmpty to handle empty Result/Error without allocations

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Co-authored-by: Aleksei Strukov <[email protected]>
Co-authored-by: Ed Zynda <[email protected]>

* feat: implement MCP elicitation support (#413)

* Add ElicitationRequest, ElicitationResult, and related types to mcp/types.go
* Implement server-side RequestElicitation method with session support
* Add client-side ElicitationHandler interface and request handling
* Implement elicitation in stdio and in-process transports
* Add comprehensive tests following sampling patterns
* Create elicitation example demonstrating usage patterns
* Use 'Elicitation' prefix for type names to maintain clarity

* Address review comments and auto-format

* Address further minor review comments

* Add sentinel errors

* Revert sampling formatting changes

* Update elicitation response to match spec

Updating elicitation response to match MCP spec document https://modelcontextprotocol.io/specification/draft/client/elicitation

* feat(streamable_http): elicitation request

Author: Ghosthell

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Co-authored-by: Ramon Nogueira <[email protected]>
Co-authored-by: Miguel <[email protected]>