Thrown from a health indicator to signal a failed check. The causes
payload is forwarded to the /health response so callers can inspect
which indicator failed and why. causes is intentionally typed as
any (matching terminus) so handlers can pass through arbitrary
upstream error payloads (HTTP responses, DB driver errors, etc.)
without forcing them to conform to HealthIndicatorResult.
The isHealthCheckError flag is a cross-realm discriminator (more
reliable than instanceof when multiple copies of the class can
exist) and is part of the public contract inherited from terminus.