Closes gh-20621

* pr/20617:
  Polish "Fix @FlywayDataSource with multiple data sources"
  Fix @FlywayDataSource with multiple data sources

Closes gh-20617

See gh-20617

See gh-20617

Closes gh-20619

Closes gh-20618

Closes gh-19564

Closes gh-20616

Closes gh-20615

Previously, the presence of a `ConsumerFactory` bean would make the
auto-configured one to back off, leading to a failure down the line if
no available instance matches the generics criterion. This commit
improves the auto-configuration to create a `ConsumerFactory<?,?>`
behind the scenes if none is available.

Closes gh-19221

Closes gh-20613

See gh-20570

Closes gh-20612

* pr/20523:
  Polish "Configure signature algorithm when using public key jwt decoder"
  Configure signature algorithm when using public key jwt decoder

Closes gh-20523

See gh-20523

See gh-20523

* gh-20608:
  Fix "Building Docker Images" section level

Closes gh-20608

See gh-20608

Closes gh-20607

* pr/20604:
  Polish BindableTests

Closes gh-20604

See gh-20604

* pr/20601:
  Remove redundant MockitoAnnotations.initMocks()

Closes gh-20601

See gh-20601

Closes gh-20600

This commit upgrades the algorithm when trailing slash are to be
ignored. Previously a root URI (i.e. "/") would result to to empty
string which is an issue for monitoring system that requires tag values
to be non empty. If the URI is a single character, the trailing is not
applied and "/" is left as is.

Closes gh-20536

Closes gh-20599

Closes gh-20578

This commit moves the core Liveness and Readiness support to its own
`availability` package. We've made this a core concept independent of
Kubernetes.

Spring Boot now produces `LivenessStateChanged` and
`ReadinessStateChanged` events as part of the typical application
lifecycle.

Liveness and Readiness Probes (`HealthIndicator` components and health
groups) are still configured only when deployed on Kubernetes.

This commit also improves the documentation around Probes best practices
and container lifecycle considerations.

See gh-19593

* gh-20585:
  Upgrade to Gradle 6.3 RC4

Closes gh-20585

See gh-20585

Closes gh-20590

Closes gh-20589

* gh-20583:
  Link to correct factory in TomcatReactiveWebServerFactory's javadoc

Closes gh-20583

See gh-20583

Closes gh-20588

Closes gh-20587

* gh-20577:
  Only suggest Ubuntu versions available in the Docker registry

Closes gh-20577

See gh-20577