Internal GitLab connection fails with unhelpful "request failed" error

[ktdreyer]

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Problem

ValidateGitHubToken, ValidateGitLabToken, and ValidateGoogleToken in components/backend/handlers/integration_validation.go discard the underlying network error and return a generic "request failed". This hides the root cause — TLS errors, DNS failures, connection refused, timeouts — from both users and operator logs.

Steps to reproduce

1. Deploy the latest version of the platform.
2. Go to Settings → Integrations → GitLab.
3. Enter a valid PAT for an internal GitLab instance (e.g. https://gitlab.cee.redhat.com).
4. Click Connect.

Actual result

GitLab connectivity check failed: failed to connect to GitLab API at https://gitlab.cee.redhat.com: request failed

Expected result

An actionable error that includes the network-level cause, e.g.:

…request failed: tls: failed to verify certificate: x509: certificate signed by unknown authority

Suggested fix

The original comment says // Don't wrap error - could leak token from request details. The token is in the Authorization header, which *url.Error does not include — but the URL itself may be sensitive. Unwrap *url.Error to extract only the inner network error:

resp, err := client.Do(req)
if err != nil {
    if urlErr, ok := err.(*url.Error); ok {
        err = urlErr.Err
    }
    return false, fmt.Errorf("request failed: %w", err)
}

Important: This change is security-relevant. Unit tests must verify that the returned error contains the network-level cause (e.g. TLS, DNS) but does not expose the request URL.