Closes gh-18429

Closes gh-18428

Closes gh-18427

Closes gh-18426

Closes gh-18425

Closes gh-18424

Closes gh-18423

Closes gh-18422

Closes gh-18421

Closes gh-18420

Closes gh-18418

Closes gh-18417

Closes gh-18416

See gh-18414

Closes gh-18411

* pr/18339:
  Polish 'Apply TTL invocation caching on reactor types'
  Apply TTL invocation caching on reactor types

Closes gh-18339

Closes gh-18398

Closes gh-18409

This reverts commit 8d9e4479.

Fix package tangle in devtools by relocating `DevToolsEnablementDeducer`
to a new `system` package.

Closes gh-18393

Fix a package tangle that was introduced when we added cache bypass to
`SpringIterableConfigurationPropertySource`. Ideally we should have
been able to depend on `env` from `context` but unfortunately the
`EnvironmentPostProcessor` interface references `SpringApplication`
which needs to use the Binder.

The `isImmutable` method has now been moved to `OriginLookup` which
removes the immediate tangle.

Closes gh-18393

Polish code and relocate `RSocketServerBootstrap` from `server` to
`context` since it's really an `ApplicationContext` concern.

Closes gh-18391

Closes gh-18395

* pr/18287:
  Polish 'Add @LocalRSocketServerPort support'
  Add @LocalRSocketServerPort support

Closes gh-18287

See gh-18287

Add an appication context initializer to detect and store the
active RSocket port in the Environment under
`local.rsocket.server.port`.

Additionally add a `@LocalServerPort` that provides a convenient
alternative to `@Value`.

See gh-18287
Co-authored-by: Eddú Meléndez <eddu.melendez@gmail.com>

* pr/18374:
  Simplify pipe escaping for reference doc tables
  Avoid need to escape pipe character in reference tables

Closes gh-18374

Replace `{vbar}` with an escaped pipe character. Unfortunately
`{vbar}` does not render correctly with PDF generation.

See gh-18374

* pr/18384:
  Polish some external documentation links

Closes gh-18384

See gh-18384

* pr/18383:
  Mention Java 13 in system requirements docs

Closes gh-18383

See gh-18383

Closes gh-17999

Extract reactor specific code to an inner class to protect
against ClassNotFound exceptions if reactor is not in use.

Also add support for `Flux`.

See gh-18339

Update `CachingOperationInvoker` so that TTL caching is applied directly
to reactive types. Prior to this commit, a `Mono` would be cached, but
the values that it emitted would not.

See gh-18339

* pr/18333:
  Use ordered TaskExecutorCustomizers

Fixes gh-18333