Closes gh-19707

Closes gh-19629

See gh-19926

* pr/19926:
  Polish "Remove unnecessary leading slash in changelog locations"
  Remove unnecessary leading slash in changelog locations

Closes gh-19926

See gh-19926

See gh-19926

Closes gh-20041

* pr/19901:
  Polish contribution
  Handle message of @ResponseStatus-annotated exception with WebFlux

Closes gh-19901

See gh-19901

See gh-19901

This commit upgrades to spring javaformat 0.0.20 and Checkstyle 8.29.

This commit also upgrades to the Checkstyle maven plugin 3.1.0.

See gh-20011

Previously, only the top-level handlers were examined to find the
ContextHandlers and log the context path. If those handlers had
been wrapped, this prevented the ContextHandlers from being found
and an empty string was always logged.

When finding the context path, this commit unwraps the handler held
by a HandlerWrapper until the ContextHandler is found.

Fixes gh-19969

* pr/19961:
  Fix Gradle plugin documentation links

Closes gh-19961

See gh-19961

* pr/19944:
  Replace deprecated Concourse resource for pull requests

Closes gh-19944

See gh-19944

* pr/19956:
  Fix typo

Closes gh-19956

See gh-19956

* pr/19913:
  Upgrade CI images to Ubuntu Bionic 20200112

Closes gh-19913

See gh-19913

* pr/19880:
  Polish "Close TomcatMetrics on shutdown for cleanup"
  Close TomcatMetrics on shutdown for cleanup

Closes gh-19880

See gh-19880

See micrometer-metrics/micrometer#1424
See gh-19880

Closes gh-19639

* pr/19855:
  Polish "Encourage use of SpringBootApplication"
  Encourage use of SpringBootApplication

Closes gh-19855

See gh-19855

See gh-19855

Closes gh-19857

This commit removes references of cache infra following the move to
Micrometer. We no longer ships an infinispan specific binder so the
dependency has been removed as well.

Closes gh-19838

This reverts commit 487b9cbf.

Fixes gh-19788

Closes gh-19763

Closes gh-19710

The release did not happen in time for 2.1.12.

See gh-19649.

The JarFile was not being closed which linked a file handle and caused
a test failure on Windows.

The local variable has been renamed as, when declared in a
try-with-resources, Checkstyle was confused by the shadowing of the
jarFile field and required references to jarFile within the try-block
the be prefixed with this.

See gh-19595

Closes gh-19761

Closes gh-19641

Closes gh-19734

Closes gh-19733

Closes gh-19732