* gh-5059:
  Remove Docker container after launch script test execution

Closes gh-5059

Closes gh-5103

* pr/4188:
  Polish contribution
  Add support of Jackson in Jersey

Closes gh-4188

If Jackson is configured for the project, the `ObjectMapper` is now
reused and added in the Jersey's context.

Closes gh-4131

Closes gh-5083

See gh-5083

See gh-5083

See gh-5083

See gh-5083

See gh-5083

See gh-5083

See gh-5083

See gh-5083

See gh-5083

Add AssertJ as a managed dependency and also include it in
spring-boot-starter-test. Also provide a simple adapter class to allow
Hamcrest matchers to be used as AssertJ Conditions.

Fixes gh-5048

Update DataSourceAutoConfiguration so that pooled datasource
configurations are only loaded via an @Import. If left as nested
classes, the load order is JVM specific and can result in the wrong
configuration being loaded.

Closes gh-2183

Previously, the Launcher was creating a new runner thread that would
call the application's main method. An exception thrown by this thread
is handled differently to one thrown by the JVM's main thread leading
to different exit behaviour. Furthermore, the separate thread isn't
actually necessary.

This commit removew the use of a separate runner thread from the
Launcher. This means that the JVM's exit behaviour will be consistent
and also removes the overhead of createing a starting an extra thread.

Closes gh-5006

Previously, BeanDefinitionLoader declared a field of type
GroovyBeanDefinitionReader which is a GroovyObject subclass. This is
problematic as BeanDefinitionLoader is always loaded but Groovy is an
optional dependency. Even on a JVM where class verification is performed
lazily, this can still cause problems if something reflectively tries
to access the class’s declared fields. On a JVM where classes are
verified at load time, it would be impossible to start a Spring Boot
application without having Groovy on the classpath.

This commit changes the field to be a BeanDefinitionReader, removing
the indirect reference to GroovyObject form BeanDefinitionLoader’s
signature. The reader is downcast to a GroovyBeanDefinitionReader in the
body of a method body that will only be invoked when Groovy is on the
classpath.

Closes gh-5040

Update SpringBootJoranConfiguratorTests to ensure that logback
is left in a sane state. Prior to this commit, running all tests
in eclipse would fail due to ErrorPageFilterTests expecting
specific log output.

* pr/5075:
  Fix MariaDB driver class name

Closes gh-5075

Previously, Spring Boot mapped both `DataSourceProperties` and the actual
`DataSource` implementation to the same prefix. This results in a huge
amount of keys in the `spring.datasource` namespace  with no way to
identify those that are valid for the pooled data source in use.

This commit maps the four pooled data sources we support in four isolated
namespace, keeping `spring.datasource` only for the common settings.

These are `spring.datasource.tomcat`, `spring.datasource.hikari`,
`spring.datasource.dbcp` and `spring.datasource.dbcp2` for the Tomcat,
Hikari, Commons DBCP and Commons DBCP2 implementations respectively.

Closes gh-2183

Closes gh-5025

* pr/5060:
  Add ref to Google gRPC starter

Closes gh-5060

* pr/5067:
  Fix typos