fix: properly implement token exchange for discovery

[yrobla]

when using the discovered mode on vmcp, we discovered that it was not working for several problems. Add a fix and add proper testing to validate

Large PR Justification

This is a complete fix of the feature, including unit tests. The fixes are atomic and need to come together to solve the issue

[github-actions]

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[codecov]

Codecov Report

❌ Patch coverage is 43.90244% with 46 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.44%. Comparing base (c73c5ef) to head (7cf6767).

Files with missing lines	Patch %	Lines
...perator/controllers/virtualmcpserver_vmcpconfig.go	42.46%	35 Missing and 7 partials ⚠️
pkg/vmcp/client/client.go	55.55%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2769      +/-   ##
==========================================
- Coverage   56.48%   56.44%   -0.05%     
==========================================
  Files         319      319              
  Lines       30943    31022      +79     
==========================================
+ Hits        17479    17510      +31     
- Misses      11960    12000      +40     
- Partials     1504     1512       +8     

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[Copilot]

Pull request overview

This PR fixes token exchange for discovery mode in the Virtual MCP (vmcp) system by addressing configuration format issues and adding comprehensive end-to-end testing with mock servers deployed as Kubernetes resources.

Key Changes:

• Fixes vmcp configuration YAML format conversion to use a flat token_cache.config structure instead of separate memory/redis sections, aligning with the YAML loader's expected format
• Adds discovery logic for incoming OIDC configuration from backend MCPServers, enabling vMCP to authenticate to backends that require OIDC
• Implements comprehensive E2E tests with mock HTTP, OAuth token exchange, and OIDC servers deployed as Kubernetes pods to validate authentication flows

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
test/e2e/thv-operator/virtualmcp/virtualmcp_auth_discovery_test.go	Replaces simple httptest mock with Kubernetes-deployed mock servers (HTTP, OAuth, OIDC) for realistic E2E testing of auth discovery and token exchange flows
test/e2e/thv-operator/virtualmcp/helpers.go	Adds GetPodLogs helper function to retrieve logs from specific pods for debugging test failures
test/e2e/oidc_mock.go	Implements proper JWKS endpoint with RSA public key export and adds client_credentials grant type support
pkg/vmcp/workloads/k8s.go	Adds discoverIncomingOIDCConfig method to discover and populate OIDC configuration from backend MCPServers, enabling vMCP→backend authentication
pkg/vmcp/types.go	Adds IncomingOIDCConfig field to Backend and BackendTarget types for storing discovered OIDC configuration
pkg/vmcp/registry.go	Propagates IncomingOIDCConfig field when converting Backend to BackendTarget
cmd/thv-operator/controllers/virtualmcpserver_vmcpconfig.go	Implements convertToCLIFormat to transform Go config structs into vmcp CLI-compatible YAML format with flat token_cache.config structure

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Large PR justification has been provided. Thank you!

[github-actions]

✅ Large PR justification has been provided. The size review has been dismissed and this PR can now proceed with normal review.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

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