Fix WPCOM API partner token validation for client credentials

[budzanowski]

Summary

Fixes WPCOM API health checks that are failing after switching from OAuth to client credentials in INTEGRA-48. The system incorrectly reports partner token as unhealthy, causing authorization status to be set to 'error' and blocking functionality.

Root Cause

• WPCOM's /wc/partners/google/remote-site-status endpoint still validates OAuth-based partner tokens
• Returns is_partner_token_healthy: false for client credentials authentication
• Causes get_connected_status() to set WPCOM_REST_API_STATUS to 'error' instead of 'approved'
• Results in broken UI states and blocked notifications/sync functionality

Changes Made

1. Fix partner token health check in AccountService::is_wpcom_api_status_healthy()

• Inject is_partner_token_healthy: true when WPCOM returns false
• Preserve existing logic for future compatibility
• Add comment explaining temporary fix until INTEGRA-50 updates WPCOM API

2. Auto-set WPCOM_REST_API_STATUS to 'approved' in AccountService::get_connected_status()

• Set status to 'approved' by default when not set (since authorization is automatic with client credentials)
• Preserve code structure for future UI functionality that may allow user control
• Fixes "NOT SET" status in debug interfaces

Impact

• ✅ Unblocks NotificationsService functionality
• ✅ Fixes Merchant Center account connection status
• ✅ Resolves UI showing incorrect "Grant access" buttons
• ✅ Ensures system works properly with client credentials from INTEGRA-48

Technical Notes

• These are temporary compatibility fixes until INTEGRA-50 updates WPCOM API
• Code preserved for future UI functionality allowing user management of these settings
• Maintains all existing security and health checks except the problematic partner token validation

Test Plan

• Verify Connection Test page shows 'approved' instead of 'NOT SET'
• Confirm NotificationsService.is_ready() returns true
• Test that Merchant Center account shows proper connected state
• Ensure no "Grant access" buttons appear inappropriately
• Verify product sync and notifications work correctly

Related Issues

• Addresses: INTEGRA-51
• Fixes issues introduced by: INTEGRA-48
• Coordinates with: INTEGRA-50 (WPCOM API updates)

🤖 Generated with Claude Code

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 66.2%. Comparing base (683dc35) to head (5d5b24c).
Report is 6 commits behind head on test/combined-branches.

Files with missing lines	Patch %	Lines
src/MerchantCenter/AccountService.php	60.0%	2 Missing ⚠️

Additional details and impacted files

@@                    Coverage Diff                     @@
##             test/combined-branches   #2985     +/-   ##
==========================================================
- Coverage                      66.2%   66.2%   -0.0%     
- Complexity                     4828    4831      +3     
==========================================================
  Files                           490     490             
  Lines                         20539   20544      +5     
==========================================================
+ Hits                          13592   13595      +3     
- Misses                         6947    6949      +2     

Flag	Coverage Δ
php-unit-tests	66.2% <60.0%> (-<0.1%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/MerchantCenter/AccountService.php	93.5% <60.0%> (-0.6%)	⬇️

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