See gh-3696

Closes gh-3423

This commit adds support for using the environment to configure the
Freemarker and Velocity view resolvers to allow session overrides.

Closes gh-3410

Closes gh-3421

Following the changes made to combines the /links and /hal endpoints
into a single /actuator endpoint, a web browser accessing /actuator
would receive a 406 response if HAL browser was not on the classpath.

This commit updates the /actuator main entry point so that it will
serve JSON to a web browser when HAL browser is not on the classpath.

The actuator's embedded documentation has also been updated to reflect
the recent changes.

Closes gh-3696

The annotation processor detects `@ConfigurationProperties` bean or
method definition and merges manual meta-data. The former step will fail
with a NPE if the annotation is not present on the classpath. This could
happen if the annotation processor is added to a module that is not
actually using Spring Boot.

We now have a defensive check that skips that steps but still attempts to
merge manual meta-data if present.

Closes gh-3720

See gh-3696

For some reason, we forgot to add an attribute to customize the package
name when using spring init. This is now the case.

Closes gh-3716

See gh-3569

Fixes gh-3527

Closes gh-3569

This commit provides a single endpoint, /actuator, that serves HTML
(the HAL browser) or JSON depending on the request’s accept header
that enables discovery of all of the actuator’s other endpoints.

When the management context path is configured, the /actuator endpoint
moves to the configured path, e.g. if the management context path is
set to /management, the actuator endpoint will be available from
/management.

Closes gh-3696

See gh-3539

See gh-3557

Closes gh-3715

Closes gh-3700

Improve the documentation on using two entity managers if Spring Data is
used.

Closes gh-3433

Make it more clear that the `ErrorPage` path requires an URL mapping to
be registered.

Closes gh-3698

See gh-3684

Closes gh-3643

Closes gh-3652

Closes gh-2671

This commit adds a new property, logging.exception-conversion-word,
that can be used to configure the conversion word that is used when
logging exceptions. The default value, %rEx, will log exceptions
with the root cause first and include class packaging information in
the stack trace. The new property is supported when using either
Logback or Log4J2.

Closes gh-3684

Upgrade documentation for the `hal` and `links` endpoints as they are
not using the root anymore.

Closes gh-3621

Update LinksMvcEndpoint and HalBrowserMvcEndpoint so that no longer try
to use the `/` context path. Links are now available from `/links` and
the HAL browser is available from `/hal`.

The actuator HAL browser now works with either WebJars or the Spring
Data version. It also now transforms the initial HTML so that the
form is pre-populated with `/links`.

When using Spring Data's HAL browser, the root includes a link to
`/links` with a rel of `actuator`.

See gh-3621

Replace `Link :` prefixes in the restdoc headings with link icons next
to the HTTP request. This fixes render issues with the titles and allows
the TOC to still function correctly.

Fixes gh-3689

Update `spring-boot-actuator-docs` to generate rest documentation in
the compile phase.

Add a new `@ImportAutoConfiguration` annotation that can be used by
tests that wish to selectively import certain auto-configuration
classes. Also add `@AutoConfigurationPackage` so that package
registration is decoupled from `@EnableAutoConfiguration`.

An added benefit of the change is @EnableAutoConfigurationImportSelector
can now be subclassed to provide custom annotation support if needed.

Fixes gh-3660
See gh-2772