SOLR-18500: Single-quote the URL in every curl example

[serhiy-bzhezytskyy]

https://issues.apache.org/jira/browse/SOLR-18500

Description

Of 510 curl commands in the Ref Guide, the URL is single-quoted in 161, double-quoted in 89 and unquoted in 190. Eleven of the unquoted ones cannot be copied as written: the shell ends the URL at & or reads <signature> as a redirect.

Solution

Every URL is single-quoted, except the 6 that need shell escapes or $VAR expansion, and the v2 API page, which SOLR-18499 rewrites. -X GET and -XPOST next to -d are dropped, and -X POST in the -T example moves before the URL.

Written with Claude Code.

Tests

For each of the 263 commands that only changed quotes, bash passes curl the same arguments before and after. The 11 unquoted ones now pass the whole URL. buildLocalAntoraSite and checkSiteLinks pass.

Checklist

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• I have created a Jira issue and added the issue ID to my pull request title.
• I have given Solr maintainers access to contribute to my PR branch. (optional but recommended, not available for branches on forks living under an organisation)
• I have developed this patch against the main branch.
• I have run ./gradlew check.
• I have added tests for my changes.
• I have added documentation for the Reference Guide
• I have added a changelog entry for my change

[epugh]

I'd love another set of eyes. Here is what we had:

And after this change:

We need to wrap certain urls that have & characters etc. But if we don't have that, should we still wrap them in single quotes? I like that we use single quotes everywhere, instead of a mix of single and double quote.. But maybe we don't want quotes on simpler URLs?

WOuld love another opinion on what looks best!

[epugh]

@janhoy @gerlowskija would love your opinon on the visual look of these CURL commands, see the one above!