See gh-18536

Closes gh-18660

* pr/18604:
  Optimize debug level logs

Closes gh-18604

See gh-18604

* pr/18665:
  Polish

Closes gh-18665

See gh-18665

* gh-18648:
  Test the Gradle Plugin against Gradle 5.6.3

Closes gh-18648

See gh-18648

See gh-18473

Prior to this commit, all supported servers would share the same
configuration property `server.connection-timeout`. Unfortunately, in
many cases the behavior of this timeout changes depending on the server.
From actual connection setup timeout, to detecting and closing idle
connections, this property cannot be properly translated from one server
implementation to another.

This commit deprecates this configuration property and introduces server
specific properties:

* `server.jetty.connection-idle-timeout`
(Time that the connection can be idle before it is closed.)
* `server.netty.connection-timeout`
(Connection timeout of the Netty channel.)
* `server.tomcat.connection-timeout`
(Amount of time the connector will wait, after accepting a connection,
for the request URI line to be presented.)
* `server.undertow.no-request-timeout`
(Amount of time a connection can sit idle without processing a request,
before it is closed by the server.)

`server.connection-timeout` is now deprecated and will be removed in a
future release.

Fixes gh-18473

* pr/18612:
  Use LinkedHashSet for deterministic order in test assertion

Closes gh-18612

See gh-18612

Closes gh-18607

See gh-18229

* pr/18581:
  Polish "Add metadata entry for spring.main.register-shutdown-hook"
  Add metadata entry for spring.main.register-shutdown-hook

Closes gh-18581

See gh-18581

See gh-18581

* pr/18578:
  Polish "Clarify formatting recommendations for configuration property javadoc"
  Clarify formatting recommendations for configuration property javadoc

Closes gh-18578

See gh-18578

This commit adds a note to spring-boot-features.adoc to clarify that
using javadoc tags to format configuration property descriptions is not
supported.

See gh-18578

* pr/18580:
  Use LinkedHashSet for deterministic order in test assertions

Closes gh-18580

See gh-18580

* pr/18579:
  Rename tests to match Surefire expectations

Closes gh-18579

See gh-18579

* gh-18575:
  Make the logger static final

Closes gh-18575

See gh-18575

* pr/18546:
  Fix incorrect backslash escape in documentation sample

Closes gh-18546

See gh-18546

* gh-18539:
  Remove accidental usage of UnsupportedOptionException

Closes gh-18539

See gh-18539

Fixes gh-18410

Previously, Maven's default behaviour was relied up which resulted
in the artifact ID being appended to each URL as it was inherited.
This behaviour can only be disabled in Maven 3.6 and later, a version
that we cannot use due to an incompatibility with the Flatten Plugin.

This commit works around Maven's default behaviour by defining
properties for the SCM URL, connection, and developer connection and
then explicitly defining the settings in each pom using these
properties. The explicit definition of the properties in each pom
prevents them being inherited from the parent, thereby disabling the
unwanted appending of the artifact ID to the URL.

Fixes gh-18328

Update `JerseyManagementContextConfiguration` so that customizer beans
are not longer applied. The endpoint resource endpoints are now added
with a registrar bean `@PostConstruct` method.

Prior to this commit, when running the management server on a different
port a `Resource` added by a customizer could be added two different
`ResourceConfig` instance. This breaks the singleton contract expected
by Jersey.

Fixes gh-17801
Co-authored-by: Phillip Webb <pwebb@pivotal.io>

Along the way, this commit also fixes a typo.

Closes gh-18325

Closes gh-18466

Closes gh-18465

See gh-18315

Closes gh-18312