This commit extract spring-related links and recurring external links
into asciidoctor attributes to be used by the Antora toolchain.
It notably homogenizes links to:
- IETF RFCs
- Java Community Process JSRs
- the Java API Documentation (on the Java 17 version)
- Kotlin documentations (on the Kotlinlang.org version)
- the Spring Boot reference guide (on the `html` version)
This commit also reworks most link attributes to follow a
Project-Category-Misc syntax. For example, `spring-boot-docs` rather
than `docs-spring-boot`.
Finally, it makes an effort to clean up remainders from the previous
documentation toolchain, namely the `docs/asciidoc` folder and
`modules/ROOT/pages/attributes.adoc` file.
Closes gh-26864
Closes gh-31619
Previously the documentation assumed that the readers knew how to use
the X-Forwarded-* headers. This commit documents details & examples
of how to use the X-Forwarded-* headers.
See gh-31491
This commit improves the documentation for the
`ShallowEtagHeaderFilter`, stating that it is only meant to support a
subset of conditional HTTP requests: GET requests with "If-None-Match"
headers. Other headers and state changing HTTP methods are not supported
here, as the filter only operates on the content of the response and has
no knowledge of the resource being served.
Closes gh-30517
