Add CaptureCommandOutputOnError

to include stdout & stderror in failed executions,
with docs.

webhook.go

@@ -282,9 +282,13 @@ func hookHandler(w http.ResponseWriter, r *http.Request) {
 				response, err := handleHook(matchedHook, rid, &headers, &query, &payload, &body)
 
 				if err != nil {
-					w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 					w.WriteHeader(http.StatusInternalServerError)
-					fmt.Fprintf(w, "Error occurred while executing the hook's command. Please check your logs for more details.")
+					if matchedHook.CaptureCommandOutputOnError {
+						fmt.Fprintf(w, response)
+					} else {
+						w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+						fmt.Fprintf(w, "Error occurred while executing the hook's command. Please check your logs for more details.")
+					}
 				} else {
 					fmt.Fprintf(w, response)
 				}