Feat: Add Gateway API support to Helm chart

[teemow]

Summary

Adds optional Gateway API (HTTPRoute) configuration to the Helm chart, allowing users to expose the service using Gateway API instead of or alongside traditional Ingress resources.

Closes #206

Changes

New Templates

• templates/httproute.yaml: Gateway API v1 HTTPRoute with:

  • Required parentRefs validation (fails early with clear error message)
  • Support for custom hostnames, matches, filters, and timeouts
  • Default PathPrefix / rule when no custom rules specified
  • Consistent template style with ingress.yaml

• templates/backendtrafficpolicy.yaml: Envoy Gateway BackendTrafficPolicy for timeout configuration

  • Default 300s timeout for long-running MCP sessions
  • Only created when both gatewayAPI.enabled and backendTrafficPolicy.enabled are true

Configuration

• values.yaml: Added gatewayAPI section with comprehensive documentation
• values.schema.json: Added schema validation for Gateway API configuration
• README.md: Updated with Gateway API documentation and examples
• Chart.yaml: Bumped version to 0.1.1

Testing

• tests/gateway_api_test.yaml: 24 comprehensive Helm unit tests covering:
  • HTTPRoute creation and conditional rendering
  • parentRefs validation failure
  • Filters and timeouts in custom rules
  • BackendTrafficPolicy dual-flag requirements
  • Service reference validation
  • Custom labels/annotations propagation

Example Usage

gatewayAPI:
  enabled: true
  httpRoute:
    parentRefs:
      - name: internal
        namespace: envoy-gateway-system
    hostnames:
      - muster.example.com
    rules:
      - matches:
          - path:
              type: PathPrefix
              value: /api
        filters:
          - type: RequestHeaderModifier
            requestHeaderModifier:
              add:
                - name: X-Custom-Header
                  value: custom-value
        timeouts:
          request: 30s
  backendTrafficPolicy:
    enabled: true
    timeout: "300s"

Migration

Both Ingress and Gateway API can be enabled simultaneously for migration scenarios.

Testing

All 45 Helm unit tests pass (24 new Gateway API tests + 21 existing tests).

[teemow]

Alignment with mcp-kubernetes Implementation

I've been working on aligning the Gateway API implementations across our Helm charts. After comparing this PR with the mcp-kubernetes implementation, here are the recommended changes to ensure consistency:

1. Add parentRefs Validation (Recommended)

mcp-kubernetes has validation that fails early if parentRefs is empty when Gateway API is enabled. This provides better user feedback:

{{- if not .Values.gatewayAPI.httpRoute.parentRefs }}
{{- fail "gatewayAPI.httpRoute.parentRefs is required when gatewayAPI.enabled is true. Specify at least one parent Gateway reference." }}
{{- end }}

2. Support Both Filters AND Timeouts

Currently this PR supports .timeouts in rules. Consider also adding .filters support for request/response modification:

{{- if .filters }}
filters:
  {{- toYaml .filters | nindent 8 }}
{{- end }}

3. Add Default Match Fallback (Already Implemented)

This PR correctly falls back to PathPrefix / when custom rules don't specify matches.

4. Reference Implementation

The unified implementation in mcp-kubernetes now supports:

• Per-resource labels/annotations (httpRoute.labels, httpRoute.annotations, backendTrafficPolicy.labels, backendTrafficPolicy.annotations)
• Validation for required parentRefs
• Both .filters and .timeouts in custom rules
• Default PathPrefix / fallback for rules without matches

See: mcp-kubernetes feature branch

Let me know if you'd like me to update this PR with these changes.

[teemow]

Addressed all recommendations from the alignment review:

Changes Made

1. parentRefs Validation - Added early validation that fails with a clear error message if parentRefs is empty when Gateway API is enabled:

   gatewayAPI.httpRoute.parentRefs is required when gatewayAPI.enabled is true. Specify at least one parent Gateway reference.
   

2. Filters Support - Added .filters support alongside .timeouts in custom rules for request/response modification:

   rules:
     - matches:
         - path:
             type: PathPrefix
             value: /api
       filters:
         - type: RequestHeaderModifier
           requestHeaderModifier:
             add:
               - name: X-Custom-Header
                 value: custom-value
       timeouts:
         request: 30s

3. Updated Documentation - Updated values.yaml comments to reflect filters support and mark parentRefs as REQUIRED

4. Test Coverage - Added 4 new tests covering:

   • Validation failure when parentRefs is empty
   • Filters in custom rules
   • Timeouts in custom rules
   • Both filters and timeouts in the same rule

All 45 Helm unit tests pass.