- Add maxInMemorySize property to Decoder and HttpMessageReader
  implementations that aggregate input to trigger
  DataBufferLimitException when reached.

- For codecs that call DataBufferUtils#join, there is now an overloaded
  variant with a maxInMemorySize extra argument. Internally, a custom
  LimitedDataBufferList is used to count and enforce the limit.

- Jackson2Tokenizer and XmlEventDecoder support those limits per
  streamed JSON object.

- Configurable limits for multipart requests with Synchronoss NIO.

- Centralized maxInMemorySize exposed via CodecConfigurer along with
  ability to plug in an instance of MultipartHttpMessageWrite.

Closes gh-23884

This commit updates URLs to prefer the https protocol. Redirects are not followed to avoid accidentally expanding intentionally shortened URLs (i.e. if using a URL shortener).

# Fixed URLs

## Fixed Success
These URLs were switched to an https URL with a 2xx status. While the status was successful, your review is still recommended.

* [ ] http://www.apache.org/licenses/ with 1 occurrences migrated to:
  https://www.apache.org/licenses/ ([https](https://www.apache.org/licenses/) result 200).
* [ ] http://www.apache.org/licenses/LICENSE-2.0 with 6515 occurrences migrated to:
  https://www.apache.org/licenses/LICENSE-2.0 ([https](https://www.apache.org/licenses/LICENSE-2.0) result 200).

Issue: SPR-17345

1. Helper method to eliminate duplication in formatting (de-)serialized
   values for logging introduced with prior commit #e62298.

2. Helper method for TRACE vs DEBUG logging with different details.

Issue: SPR-17254

Issue: SPR-17254

At DEBUG show up to 100 chars, at TRACE show full formatted value.

Note that the formatValue helper method is duplicated a number of times
in this commit. A utility method will likely be added in spring-core
through an extra commit.

Issue: SPR-17254

Issue: SPR-17086

Issue: SPR-17029

Issue: SPR-16966

Reorganize imports to ensure consistent ordering. This commit also
expands any `.*` static imports in favor of using fully-qualified
method references.

Issue: SPR-16968

Update code that has accidentally used spaces instead of tabs.
Also remove all trailing whitespace.

Issue: SPR-16968

Ensure that `this.` is used consistently when accessing class
fields.

Issue: SPR-16968

Issue: SPR-16898

Also, ZeroCopyHttpOutputMessage provides writeWith(Path, int, int), enforcing that variant as the implementation target in 5.1 (analogous to FilePart).

Issue: SPR-16925

Issue: SPR-16727

Issue: SPR-16639

Issue: SPR-16546

Fixed by creating `Callable`-based variants, as explained in the JIRA
issue.

Issue: SPR-16403

Issue: SPR-15748

Beyond just formally declaring the current behavior, this revision actually enforces non-null behavior in selected signatures now, not tolerating null values anymore when not explicitly documented. It also changes some utility methods with historic null-in/null-out tolerance towards enforced non-null return values, making them a proper citizen in non-null assignments.

Some issues are left as to-do: in particular a thorough revision of spring-test, and a few tests with unclear failures (ignored as "TODO: NULLABLE") to be sorted out in a follow-up commit.

Issue: SPR-15540

Issue: SPR-15540

Issue: SPR-15515

The MultipartHttpMessageWriter now directly encodes part header values
defaulting to UTF-8 and also specifies the charset in the
Content-Type header for the entire request.

This should work with something commonly used like Apache Commons
FileUpload which checks request.getCharacterEncoding() and uses it
for reading headers.

Issue: SPR-14546

This commit turns the Synchronoss NIO Multipart HttpMessageReader into
a reader of Flux<Part> and creates a separate reader that aggregates
the parts into a MultiValueMap<String, Part>.

Issue: SPR-14546

This commit properly closes the opened channels in the SynchronossPart,
and also makes sure that the entire contents is copied, not just the
first batch.

This commit introduces reactive multipart support by adding a new
MultipartHttpMessageReader interface (with default methods) and a
SynchronossMultipartHttpMessageReader implementation based on
the Synchronoss NIO Multipart implementation
(https://github.com/synchronoss/nio-multipart).

Issue: SPR-14546