This service is used to register health indicator functions which, before v3.6.0, were run by the
/health endpoint. Since v3.6.0 registered indicators are not executed, and this service will be
removed in v4.0.0. See the health checks guide.
The example below shows how a plugin registered an indicator before v3.6.0:
Example
(fn: HealthIndicatorFunction | HealthIndicatorFunction[]) => Registers one or more HealthIndicatorFunctions. Since v3.6.0 the registered functions are never called.