Closes gh-10647

* pr/10657:
  Remove "Securing the H2 console" section

Closes gh-10657

* pr/10658:
  Polish "Use Assert.state() with Supplier where possible"
  Use Assert.state() with Supplier where possible

Closes gh-10658

See gh-10658

* pr/10636:
  Polish

Closes gh-10636

Previously, the media types that are consumed and produced by
endpoints were configured in the web stack-specific configuration.
Furthermore, these configured media types were not used for the
discovery "endpoint" that links to all the available endpoints.

This commit introduces EndpointMediaTypes that is configred in a
single, central location and then used to configure the consumed and
produced media types for endpoints exposed via WebFlux, Web MVC, and
Jersey as well as the discovery "endpoint" provided by each.

Closes gh-10659

* pr/9737:
  Polish "When pool autocommit is disabled, inform Hibernate"
  When pool autocommit is disabled, inform Hibernate

Closes gh-9737

Starting with Hibernate 5.2.10, the JPA property
`hibernate.connection.provider_disables_autocommit` should be set to true
when the datasource has autocommit disabled in order to improve
performance.

See gh-9737

* pr/10609:
  Update docs for OpenShift

The current documentation references mechanisms for OpenShift 2, which
has been changed significantly with the latest releases, specifically the
OpenShift 3 release.

Closes gh-10609

* pr/10616:
  Fix broken links

Closes gh-10616

* pr/10615:
  Use properties in Security OAuth2 Client doc config example
  Fix Security OAuth2 Client documentation

Closes gh-10615

This commit fixes incorrect section level and sample configuration properties.

See gh-10615

Also, move properties corresponding to management server under
`management.server.*`.

Closes gh-10230

This commit adds support for Spring Boot error conventions with WebFlux.
The Spring MVC support for that is based on an `Controller` that's
mapped on a specific `"/error"` path and configured as an error page in
the Servlet container. With WebFlux, this support leverages a
`WebExceptionHandler`, which catches exceptions flowing through the
reactive pipeline and handles them.

The `DefaultErrorWebExceptionHandler` supports the following:
* return a JSON error response to machine clients
* return error HTML views (templates, static or default HTML view)

One can customize the error information by contributing an
`ErrorAttributes` bean to the application context.

Spring Boot provides an `ErrorWebExceptionHandler` marker interface and a
base implementation that provides high level constructs to handle
errors, based on the Spring WebFlux functional flavor.
The error handling logic can be completely changed by providing a custom
`RouterFunction` there.

Fixes gh-8625

Closes gh-10515

Closes gh-10651

* gh-10635:
  Fix typo in documentation

- As error handling sample is using `CustomErrorType`, fix
  description which mentions `CustomerErrorType`.

Previously, the custom layout sample did not configure the source
and target for the compiler. This meant that both defaulted to 1.5
which is not supported by Java 9's javac. The oldest support version
is 1.6.

This commit sets the maven.compiler.source and maven.compiler.target
properties to 1.8 (the lowest version support by Boot 2.0) allowing
the sample to build with both Java 8 and Java 9.

See gh-10515

See gh-10515

See gh-10515

Closes gh-10632

Closes gh-10631

Closes gh-10630

Closes gh-10629