fix: Middleware Pipeline — Closure Captures Wrong Request

[s2x]

Summary

Fixes a critical bug in the middleware pipeline where middleware modifications to the request object were not propagating to subsequent middleware in the chain.

Problem

In HttpRequestHandler, the closure in the middleware loop was capturing $request from the outer scope instead of using the $input parameter:

// Before (buggy)
$next = fn(Request $input): Http\Response => $middleware($request, $next);

This caused all middleware to receive the original request, ignoring any modifications made by previous middleware.

Solution

Changed the closure to use the $input parameter:

// After (fixed)
$next = fn(Request $input): Http\Response => $middleware($input, $next);

Testing

Added comprehensive tests in MiddlewarePipelineTest.php that verify:

1. Middleware can modify request headers
2. Subsequent middleware sees the modified request
3. The fix works correctly with 3+ middleware in the chain

Breaking Changes

None.

References

• Closes Bug in Middleware Pipeline — Closure Captures Wrong Request #21