feat: add HTTPError type for non-200 Grafana API responses (WH-4113)

[danielBWeka]

Summary

• Adds exported HTTPError struct to pkg/grafanadata/model.go with StatusCode int and Body string fields
• Replaces plain fmt.Errorf strings with *HTTPError on all non-200 HTTP responses across getDashboard, getPanelData, getLabelValues, getDefaultDatasource, and FetchDashboards

Backwards compatibility

Fully backwards compatible. *HTTPError implements the error interface so any caller checking err != nil or calling err.Error() is unaffected. New callers can use errors.As to extract the status code and mirror it upstream rather than returning a generic 500.

Usage

var httpErr *grafanadata.HTTPError
if errors.As(err, &httpErr) {
    // mirror httpErr.StatusCode back to the caller
}

[danielBWeka]

@cursor review

[cursor]

Skipping Bugbot: Bugbot is disabled for this repository. Visit the Bugbot dashboard to update your settings.

[Copilot]

Pull request overview

This PR introduces a typed HTTPError error for non-200 responses from the Grafana API client so callers can reliably extract the upstream HTTP status code (via errors.As) instead of parsing fmt.Errorf strings.

Changes:

• Added exported HTTPError type (status code + response body) implementing error.
• Updated Grafana client methods to return *HTTPError on non-200 HTTP responses (including reading the body first where needed).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
pkg/grafanadata/model.go	Adds exported HTTPError type implementing error with status code + body.
pkg/grafanadata/grafanadata.go	Replaces non-200 fmt.Errorf returns with *HTTPError across several client calls.
pkg/grafanadata/dashboard.go	Switches non-200 handling in FetchDashboards to return *HTTPError.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.