confluence: fix NewAPI double-slash and DeletePageLabel missing status check

NewAPI: normalize baseURL by trimming the trailing slash before building
rest and json-rpc endpoints. Previously the TrimSuffix only applied to
api.BaseURL but rest/json URLs were already constructed with the raw
(potentially trailing-slash) baseURL, producing double slashes like
'http://example.com//rest/api'.

DeletePageLabel: add a non-200/non-204 status check before the type
assertion. Without this guard any error response (400, 403, 500) would
fall through to request.Response.(*LabelInfo) and either panic or return
garbage data.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

confluence/api.go

@@ -108,6 +108,9 @@ func NewAPI(baseURL string, username string, password string, insecureSkipVerify
 		}
 	}
 
+	// Normalize baseURL once before building all derived endpoints.
+	baseURL = strings.TrimSuffix(baseURL, "/")
+
 	var httpClient *http.Client
 	if insecureSkipVerify {
 		httpClient = &http.Client{
@@ -137,7 +140,7 @@ func NewAPI(baseURL string, username string, password string, insecureSkipVerify
 	return &API{
 		rest:    rest,
 		json:    json,
-		BaseURL: strings.TrimSuffix(baseURL, "/"),
+		BaseURL: baseURL,
 	}
 }
 
@@ -665,6 +668,10 @@ func (api *API) DeletePageLabel(page *PageInfo, label string) (*LabelInfo, error
 		return nil, nil
 	}
 
+	if request.Raw.StatusCode != http.StatusOK {
+		return nil, newErrorStatusNotOK(request)
+	}
+
 	return request.Response.(*LabelInfo), nil
 }