[Initiative] Query Handler Chain of Responsibility for Standard and Extension Kinds

[juliuskrah]

Summary

Introduce a query-time Chain of Responsibility so resource reads are resolved through explicit handler stages instead of ad-hoc branching. This enables consistent behavior for standard kinds and extension-defined kinds.

In Scope

• Define a query handler pipeline with ordered stages:
  1. schema/query-shape guard
  2. standard kind resolver (core kinds)
  3. extension resolver (WASI-backed custom kinds)
  4. reference resolution/enrichment stage
• Implement deterministic stage contracts (input/output/error model) and short-circuit rules
• Add observability per stage (latency, hit-rate, failures)
• Support per-kind routing rules so standard and custom kinds can coexist
• Add tests covering core kind resolution, extension fallback, and mixed-reference resolution

Out of Scope

• Dynamic GraphQL schema generation/stitching mechanics
• Marketplace UX for extensions
• Mutating write-time admission behavior

Acceptance Criteria

• Query path runs through a documented, ordered handler chain
• Core kinds resolve through the standard handler path without extension dependency
• Custom kinds can be resolved via extension handler when registered
• Reference resolution stage can enrich final objects without changing upstream stage contracts
• Per-stage metrics/logging/tracing are emitted and actionable
• Integration tests validate stage ordering and fallback semantics

Implementation Notes

A handler chain makes query behavior explicit and composable. It avoids hard-coding kind checks across resolvers and gives a stable extension seam for non-core kinds. The design should remain level-triggered: each handler receives the current object context and either handles, enriches, or passes onward.

Dependencies

• Depends on: [Initiative] Universal ScyllaDB Resource Table for CRD-Style Resources #140 (Universal ScyllaDB Resource Table for CRD-Style Resources)
• Related: [Initiative] WASI Extension Marketplace #35 (WASI Extension Marketplace), [Initiative] Controller Watch API with resourceVersion Resume #131 (Controller Watch API), [Initiative] Object Lifecycle Versioning Contract for UID and resourceVersion #137 (Object Lifecycle Versioning Contract)

Tracking

• Area: infra
• Priority: p2 – high
• Target Milestone / Release: TBD

[juliuskrah]

Blocks: #149 (Dynamic GraphQL Schema Synthesis depends on handler chain contract). Related: #150 (Agent Orchestration Workers consume the handler pipeline).