The versions of Jackon's bom and the versions of Jackson are often
not the same. For example, at the time of writing, the latest bom
version is 2.9.9.20190807 but the latest version of Jackson's core
is 2.9.9 and the latest version of Jackson's databind is 2.9.9.3.

spring-boot-dependencies using a property, jackson.version, to control
the version of jackson-bom that is imported. To make it clear that the
version property controls the version of Jackson's bom and not of
Jackson itself, this commit deprecates jackson.version in favour of
a new jackson-bom.version property.

An additional benefit of this change is that it addresses a problem
when using Gradle and the dependency management plugin. Jackson's bom
uses a jackson.version property to control the version
of core Jackson modules. This names clashes with the name of the
property used by spring-boot-dependencies. Specifying a custom
jackson.version to control the version of the bom that is imported
would also have the unwanted side-effect of customizing the version of
the core Jackson modules declared in Jackson's bom.

Fixes gh-17808

Closes gh-17935

Fixes gh-17927

Closes gh-17905

* pr/17875:
  Remove redundant code

Closes gh-17875

See gh-17875

* pr/17861:
  Map non-null LDAP properties

Closes gh-17861

The userDn and password in LdapContextSource are not nullable. The
default values for userDn and password in LdapProperties are null. When
the values are set to null there will eventually be a
NullPointerException during
AbstractContextSource#setupAuthenticatedEnvironment since HashTable
doesn't allow null for values.

See gh-17861

* pr/17805:
  Polish "Set up SpringLiquibase beans' dependencies by type rather than name"
  Add missing javadoc
  Set up SpringLiquibase beans' dependencies by type rather than name

Closes gh-17805

See gh-17805

See gh-17805

See gh-17805

* gh-17876:
  Test the Gradle Plugin against Gradle 5.6

Closes gh-17876

See gh-17876

* pr/17780:
  Polish "Expand documentation on remote devtools"
  Expand documentation on remote devtools

Closes gh-17780

See gh-17780

See gh-17780

Fixes gh-17843

Closes gh-12874

Closes gh-17842

Closes gh-17698

Closes gh-12874

Closes gh-17835

* pr/17835:
  Fix syntax errors in docs

Closes gh-17835

See gh-17835

Closes gh-16704

Closes gh-16853

* pr/17778:
  Polish "Configure a temporary directory with Undertow"
  Configure a temporary directory with Undertow

Closes gh-17778

See gh-17778

See gh-17778

* pr/17807:
  Polish "Fix annotation lookup on proxied EndpointExtension"
  Fix annotation lookup on proxied EndpointExtension

Closes gh-17807

See gh-17807

See gh-17807