feat: add multicluster support to local-setup

[crstrn13]

Problem

Currently, make local-setup only provisions a single cluster, making it impossible to run multicluster tests locally:

• Multicluster tests skip locally due to missing second cluster
• Developers cannot test DNS, TLS, and load balancing across clusters
• Local development doesn't support multicluster scenarios
• Requires external environment to test multicluster features

Proposed Solution

1. Provision Second Cluster

Extend make local-setup to optionally create a second cluster (e.g., kind create cluster --name cluster2)

2. Configure Multicluster Networking

Set up networking between clusters:

• Configure cluster peering or gateway connectivity
• Ensure clusters can communicate with each other
• Set up DNS resolution between clusters

3. Deploy Kuadrant on Both Clusters

• Deploy Kuadrant operator and components on both clusters
• Configure multicluster gateway/route setup
• Set up shared control plane or distributed control plane as needed

4. Configure Certificate Authority

Investigation needed: Determine best approach for local CA setup:

• Option A: Generate a new self-signed CA for local development
• Option B: Import an existing CA for testing
• Consider: cert-manager configuration, trust between clusters, TLS certificate generation

5. Configure Test Settings

Update test configuration to support multicluster scenarios:

• Configure settings.local.yaml with both cluster contexts
• Set up cluster-specific kubeconfig access
• Configure DNS and service discovery for multicluster

Benefits

• ✅ Enables running multicluster test suite locally
• ✅ Developers can test DNS, TLS, and load balancing features
• ✅ Faster iteration on multicluster features
• ✅ No dependency on external multicluster environments

Acceptance Criteria

• make local-setup (with multicluster flag) provisions two clusters
• Both clusters have Kuadrant deployed and configured
• Clusters can communicate with each other (networking configured)
• CA configured (investigation determines approach: generate vs import)
• TLS certificates working across clusters
• Multicluster tests pass on local-setup: make test testsuite/tests/multicluster/
• Documentation updated with multicluster local-setup instructions
• Optional: Make target to clean up multicluster setup (make clean-multicluster)

Related

• Multicluster tests: testsuite/tests/multicluster/
• DNS tests: testsuite/tests/multicluster/coredns/
• Load balanced tests: testsuite/tests/multicluster/load_balanced/

Technical Notes

• Consider using kind clusters with custom network configuration for local multicluster
• May need MetalLB or similar for LoadBalancer services in kind
• DNS setup might require CoreDNS configuration or external DNS
• CA investigation should consider: cert-manager, trust stores, certificate rotation
• Resource requirements: running two clusters locally may be resource-intensive

Investigation Tasks

• Research best practices for local CA setup (generate vs import)
• Evaluate cert-manager configuration for multicluster
• Determine cluster trust and certificate distribution approach