Add `QUERY` Support For `application/jsonpath`

[eviltester]

Add QUERY Support For application/jsonpath

I want to send a QUERY request with a JSONPath expression body,
so that I can safely filter todo resources using a standards-based query language.

Scope

Implement QUERY /todos with:

Content-Type: application/jsonpath
Accept: application/json

The request body should be a JSONPath expression evaluated against the JSON todo collection.

Example:

QUERY /todos HTTP/1.1
Content-Type: application/jsonpath
Accept: application/json

$.todos[?@.doneStatus == false]

Expected Behaviour

• QUERY /todos is safe and idempotent.
• It must not create, update, or delete todos.
• The body is parsed as a JSONPath expression.
• The expression is evaluated against the same logical data returned by GET /todos.
• The response returns matching todo items.
• Response format is still controlled by the Accept header.
• Accept-Query should advertise support:

Accept-Query: application/jsonpath

Error Behaviour

• Missing Content-Type returns 400.
• Unsupported Content-Type returns 415.
• Invalid JSONPath syntax returns 400.
• Valid JSONPath that cannot be applied safely returns 422.
• Unsupported response Accept values still return 406.

Acceptance Criteria

• QUERY /todos with application/jsonpath can filter by doneStatus.
• It can filter by id, title, and description where JSONPath supports it.
• It returns the same todo representation shape as GET /todos.
• Repeating the same request returns the same result unless the todo data changes externally.
• OPTIONS /todos includes QUERY in Allow.
• HEAD /todos or OPTIONS /todos includes Accept-Query: application/jsonpath.