Closes gh-24025

Closes gh-22908

Closes gh-24023

Previously, when an embedded test database was being auto-configured
any schema username and password specified by the user would result
in a separate embedded test database being created to load the schema.
This then left the actual test database without the schema causing
test failures.

This commit updates the test database auto-configuration to set the
schema username to an empty string in a property source that's added
first to the environment's property sources. This causes any schema
username configured by the user to be ignored, preventing the creation
of a separate database for schema.sql processing.

Fixes gh-19321

Closes gh-24021

* gh-24020:
  Fix typo in Spring Session documentation

Closes gh-24020

See gh-24020

Closes gh-24018

Closes gh-23151

Fixes gh-23821

* gh-23999:
  Polish "Avoid repeated calls of WebFlux and MVC registrations' getters"
  Avoid repeated calls of WebFlux and MVC registrations' getters

Closes gh-23999

See gh-23999

See gh-23999

Closes gh-24014

Previously, Quartz could be configured with a specific DataSource
using `@QuartzDataSource` but it was not possible to configure a
Quartz-specific transaction manager. This could result in the
different DataSources being used by Quartz itself and Quart'z
DataSourceTransactionManager.

This commit introduces a new qualifier, `@QuartzTransactionManager`,
that can be used to avoid the above-described problem. Any
`@QuartzTransactionManager`-annotated bean will be used by the
Quartz auto-configure configuration instead of the application's main
`TransactionManager`. If no such qualified bean is present, the
application's main TransactionManager, if any, will be used as before.

Fixes gh-20184

Closes gh-24012

Fixes gh-23978

Closes gh-24009

When running on Java 11 (where `@PostConstruct` is no longer part of
the JRE) and without a dependency on jakarta-annotation-api,
`@PostContruct` annotions are silently dropped. This leads to obscure and
hard-to-track down changes in the behaviour of our auto-configuration
as the `@PostConstruct`-annotated methods are not invoked.

To allow users to run on Java 11 without having jakarta-annotation-api
on the classpath, this commit removes use of `@PostConstruct` from main
code. A Checkstyle rule has also been added to prevent its usage in
main code from being reintroduced.

Closes gh-23723

Closes gh-24006

Closes gh-23808

Closes gh-24004

Closes gh-22925

Previously, the main jar file and the source and javadoc jar files all
had the same changes applied to their manifests.

The commit changes the Implementation-Title of source and javadoc jars
so that the title indicates that's what they are. Rather than using
the project's description as the title (as is done for the main jar),
the titles for source and javadoc jars will now be "Source for
${project.name}" and "Javadoc for ${project.name}" respectively.

Closes gh-23974

Closes gh-23996

Closes gh-23991

Update `BintrayService.isDistributionComplete` to use unpublished
artifacts.

See gh-23824

Closes gh-23824

Closes gh-23969

Fixes gh-23966

Closes gh-23965