Prior to this commit, some same-page links in our Antora-based docs
were written using the `xref:` macro, which Antora resolves as a
cross-page reference. However, a same-page target can be misread as a
page reference and break the site build (as nearly happened in
gh-37152), whereas `<<id,text>>` only ever resolves against the current
page's own anchors.
To address that inconsistency and avoid potential future bugs (broken
links), this commit converts all such same-page `xref:` links to
`<<id,text>>`, leaving genuine cross-page `xref:` links are unaffected.
Closes gh-37161
This commit adds integration tests and reference documentation
for multipart support in `RestClient` and `RestTestClient`.
Closes gh-35569
Closes gh-33263
Sam Brannen
Gabriel Gerhardt
Brian Clozel
rstoyanchev
Sébastien Deleuze
Rob Worsnop