Align docs structure + drop version clutter #228

[rymsha]

Closes #228.

Brings docs/ in line with the reference enonic/lib-cors layout and drops "what was added when" clutter from the current (XP 8) docs. The 3.x (XP 7) branch is left untouched — a separate PR against 4.x will cherry-pick just the doc cleanup.

Structure

• docs/index.adoc: add NOTE: Versions 4.x target XP 8+. near the top.
• docs/versions.json: 4.x becomes stable (latest: true) with 3.x as the second entry (drops the pre-release next / master pairing).
• .github/workflows/enonic-docgen.yml: also trigger on push to 4.x, matching every branch listed in versions.json.

Clutter removed from docs/index.adoc

• image::…badge/xp-7.+… — XP 7+ shield no longer reflects the target platform (4.x is XP 8+).
• include 'com.enonic.lib:lib-http-client:3.2.1' → include "com.enonic.lib:lib-http-client:${libVersion}". The hardcoded 3.2.1 was frozen from an earlier version; the placeholder mirrors what lib-cors does.
• (added in v3.2.0) on the disableHttp2 option.
• [*v3.0.0+*] on the KeyStore and TrustStore Configuration section heading.
• Three of four bullets in == Compatibility:
  • "Not compatible with XP releases before version 7.0 …" — pre-XP 8 caveat that no longer applies (4.x is XP 8+); /lib/xp/http-client isn't a name XP core defines anyway.
  • "Starting from version 3.0.0 library uses Java HttpClient instead of OkHttp …" — describes the 2.x → 3.x transition.
  • "Starting from version 3.0.0 library uses Java Platform KeyStore …" — duplicates the KeyStore and TrustStore Configuration section above and describes a removal (clientCertificate can only be typeof Stream) that new readers don't need to know about.

Deliberately kept

• The Preemptive authentication is not supported. Use an Authorization: Basic <credentials> header instead. bullet — reworded to current tense (dropped the "Starting from version 3.0.0" prefix). This is a functional caveat readers still hit today, not a changelog note.
• KeyStore and TrustStore Configuration section body, including the WARNING about certificates / clientCertificate — current behavior.
• Compression section — current behavior.

Verify

• docs/versions.json re-parses as valid JSON.
• .github/workflows/enonic-docgen.yml re-parses as valid YAML.
• docs/index.adoc renders with asciidoc locally (same warnings as lib-cors' index.adoc in the same environment — missing source-highlight binary, not a doc problem).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.42%. Comparing base (4cfc31f) to head (f5df8ec).

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #229   +/-   ##
=========================================
  Coverage     91.42%   91.42%           
  Complexity      156      156           
=========================================
  Files             9        9           
  Lines           513      513           
  Branches         58       58           
=========================================
  Hits            469      469           
  Misses           23       23           
  Partials         21       21           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.