<!-- Provide a brief summary of your changes -->
Route `interceptors/list` and `interceptor/invoke` through the receiving
middleware chain so that middleware installed (audit, etc.) fires for
interceptor protocol methods the same way it does for standard MCP
methods.
## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
Before this change, custom JSON-RPC methods were dispatched via a
separate code path that bypassed receiving middleware entirely. This
meant any middleware an operator installed would silently not apply to
the interceptor protocol endpoints.
The fix adds `AddReceivingCustomMethod[P, R, T]` as a package-level
generic function to the vendored go-sdk/mcp package. Custom methods
registered through it are stored in a per-server customMethods map and
merged into `receivingMethodInfos()`, so `defaultReceivingMethodHandler`
dispatches them exactly like built-in methods. External types satisfy
the sealed `Params`/`Result` interfaces by embedding the
`ParamsBase`/`ResultBase` types exported from the mcp package.
## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->
Existing test suites and new ones for verifying middleware paths.
## Breaking Changes
<!-- Will users need to update their code or configurations? -->
no.
## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->
The changes to `vendor/go-sdk/mcp/server.go` are intentionally minimal
and carry a `NOTE` comment acknowledging they are additions to the
upstream SDK needed for this reference implementation.
---------
Signed-off-by: Ukjae Jeong <jeongukjae@gmail.com>
5bd7ab4d2a