Overhaul `HealthEndpoint` support to make it easier to support health
groups. Prior to this commit the `HealthIndicator` interface was used
for both regular indicators and composite indicators. In addition the
`Health` result was used to both represent individual, system and
composite health. This design unfortunately means that all health
contributors need to be aware of the `HealthAggregator` and could not
easily support heath groups if per-group aggregation is required.
This commit reworks many aspects of the health support in order to
provide a cleaner separation between a `HealthIndicator`and a
composite. The following changes have been made:
- A `HealthContributor` interface has been introduced to represent
the general concept of something that contributes health information.
A contributor can either be a `HealthIndicator` or a
`CompositeHealthContributor`.
- A `HealthComponent` class has been introduced to mirror the
contributor arrangement. The component can be either
`CompositeHealth` or `Health`.
- The `HealthAggregator` interface has been replaced with a more
focused `StatusAggregator` interface which only deals with `Status`
results.
- `CompositeHealthIndicator` has been replaced with
`CompositeHealthContributor` which only provides access to other
contributors. A composite can no longer directly return `Health`.
- `HealthIndicatorRegistry` has been replaced with
`HealthContributorRegistry` and the default implementation now
uses a copy-on-write strategy.
- `HealthEndpoint`, `HealthEndpointWebExtension` and
`ReactiveHealthEndpointWebExtension` now extend a common
`HealthEndpointSupport` class. They are now driven by a
health contributor registry and `HealthEndpointSettings`.
- The `HealthStatusHttpMapper` class has been replaced by a
`HttpCodeStatusMapper` interface.
- The `HealthWebEndpointResponseMapper` class has been replaced
by a `HealthEndpointSettings` strategy. This allows us to move
role related logic and `ShowDetails` to the auto-configure module.
- `SimpleHttpCodeStatusMapper` and `SimpleStatusAggregator`
implementations have been added which are configured via constructor
arguments rather than setters.
- Endpoint auto-configuration has been reworked and the
`CompositeHealthIndicatorConfiguration` class has been replaced
by `CompositeHealthContributorConfiguration`.
- The endpoint JSON has been changed make `details` distinct from
`components`.
See gh-17926
3c535e0de3