See gh-21002

Closes gh-21111

Closes gh-21106

Improve "@ConfigurationProperties vs. @Value" documentation with the
recommendation that kebab-case is used with the `@Value` annotation.

Closes gh-20507

Refactor `PortInUseException` logic to a single place and refine when
the exception is thrown.

Prior to this commit, we assumed that a `BindException` was only thrown
when the port was in use. In fact, it's possible that the exception
could be thrown because the requested address "could not be assigned".

We now only throw a `PortInUserException` if the `BindException` message
includes the phrase "in use".

Fixes gh-21101

Fixes gh-20866

Closes gh-20846

Closes gh-21097

Closes gh-21095

Closes gh-21087

Closes gh-21088

Closes gh-21084

Closes gh-21091

Add how-to documentation describing how health information can be
exported to a Micrometer Gauge.

Closes gh-18329

Fixes gh-20665

Closes gh-21082

Closes gh-19782

Fixes gh-21073

Closes gh-20895

Update `JarURLConnection` to ensure that when connections are opened
a new copy of the JarFile is provided.

Prior to this commit, a single `JarFile` instance was shared which meant
that it could be accidental closed if accessed via
`JarURLConnection.getJarFile()`. If the underlying jar file is closed
then it's possible for a `NoClassDefFoundError` to be thrown if running
on JDK 11 with an active `SecurityManager`.

Closes gh-17796

Closes gh-21070

Update `WebMvcAutoConfiguration` to automatically apply cors
configuration to the `WelcomePageHandlerMapping`.

Fixes gh-21048

This commit harmonizes the change made to @DefaultValue to the
annotation processor. If such annotation is added to a scalar value with
no value at all, no default value is produced.

Closes gh-18917

Closes gh-21061

Closes gh-21052

Update `NettyWebServer` so that the `PortInUseException` is not thrown
for permission denied errors.

Fixes gh-19807

Update classes that throw `PortInUseException` so that they also
include the cause. Prior to this commit the cause was not included
which could make diagnosing the real cause difficult.

See gh-19807

Fixes gh-20745

When using constructor binding, if no properties are bound to
a nested property, the top-level instance will be created with a
null value for the nested property.
This commit introduces support for an empty `@DefaultValue` which
indicates that an instance of the nested property must be created
even if nothing is bound to it. It honors any `@DefaultValue`
annotations that the nested property might have in its constructor.

Closes gh-18917

Update `ConditionalOnAvailableEndpoint` so that it now uses the same
matching code as the endpoint filter. This allows the condition to
match endpoint IDs that contain a dash.

In order to share logic, the `ExposeExcludePropertyEndpointFilter` class
has been deprecated and its logic moved to a new `expose` package
under `IncludExcludeEndpointFilter`. This filter is used by both the
`OnAvailableEndpointCondition` and the auto-configuration classes.

Fixes gh-21044

Closes gh-21039

Closes gh-21027

Update the reference documentation with more details about how relaxed
binding works against environment variables.

Closes gh-18215

Closes gh-21025

Closes gh-19972