[Update] Added Forbidden Response Check in PagerDuty Detector Verification

[nabeelalam]

Description:

Improved PagerDuty detector logic for credential validation.

Added handling for PagerDuty’s 403 Forbidden response for API tokens which are valid but do not have access to the resource:

{
  "error": {
    "message": "Access Denied",
    "code": 2010
  }
}

If the 403 response body contains the string "Access Denied" and the code "2010", the detector now treats this specific case as a successful credential validation (return true, nil).

Any other 403 response will return an unverified response with verification error since credential validity can’t be confirmed.

Checklist:

• Tests passing (make test-community)?
• Lint passing (make lint this requires golangci-lint)?