Closes gh-19782

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

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

Fixes gh-21048

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

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

Closes gh-18215

Closes gh-19972

Update `ExposeExcludePropertyEndpointFilter` so that patterns will
also match endpoint IDs that contain a dash.

Closes gh-20997

Refine `DataSourceAutoConfiguration` conditions so that an empty
`spring.datasource.url` property can be used to enable the embedded
source.

Fixed gh-20996

Closes gh-20978

Closes gh-20976

Closes gh-20623

See gh-20941

See gh-20940

See gh-20939

See gh-20938

See gh-20937

Closes gh-20678

Since the branch name doesn't always correspond to the milestone name,
eg, master.

See gh-20680

This is done by checking for existing issues only in the milestone
corresponding to the current branch. For issues, the milestone is assigned
at the time of issue creation. For PRs, since the branch is different the
milestone can be derived from that while triaging the issue.

Closes gh-20680

* pr/20756:
  Upgrade to Docker 19.03.8 in CI

Closes gh-20756

See gh-20756

* pr/20793:
  Harmonize issue title for auto-created Docker upgrade issues

Closes gh-20793

See gh-20793

If a PR with the given title exists, we clone the existing PR branch so
that it doesn't get overridden by master.

See gh-20530

See gh-20530

See gh-20530

* pr/20530:
  Polish "Automate Docker update in CI"
  Automate Docker updates in CI

Closes gh-20530

See gh-20530

See gh-20530

Closes gh-20719

This commit is a follow-up of gh-20709 to apply the same consistency
level to the Cassandra reactive health indicator.

Closes gh-20713

* pr/20709:
  Polish "Use LOCAL_ONE when querying system.local"
  Use LOCAL_ONE when querying system.local

Closes gh-20709

See gh-20709

The system keyspace has a replication factor of 1 and is local to each
node; it is therefore recommended to query system.local with a
consistency level of ONE or LOCAL_ONE.

Stronger consistency levels may result in an Unavailable error, but this
does not mean that the node is down.

See gh-20709

Previously, a condition checked the value of "spring.datasource.url" to
determine if an embedded database has to be created as a fallback. When
the value is set with an unresolved placeholder, this fails even if
the DataSource is going to created by another mean ultimately.

This commit makes a more conservative check by only checking the
presence of the property rather than its value.

Closes gh-20438

Closes gh-20624