Capped at DEFAULT_TELEMETRY_MESSAGE_LENGTH_LIMIT; see
errorMessageTruncated. The full message should always go to the log
service alongside this.
OptionalerrorMessageTruncated?: booleanPresent and true only when errorMessage was clipped. Reported rather
than left implicit so a substring search that misses can be distinguished
from one that genuinely found nothing.
OptionalhttpStatus?: numberThe response status, when the failure is a network error
The error dimensions every failure telemetry event carries, so failure rates across different actions are computed on the same fields.