[Backport 4.2.x] Support section variable in manual url (#8494)

[wangf1122]

Manuals backport for #8494

• support section variable in manual url

• isoLang variable, help wording

• Revert "isoLang variable, help wording"

This reverts commit 0b000ce

• ignore path "/" for default language replacement

• Update web-ui/src/main/resources/catalog/locales/en-admin.json

• remove double slash

• remove double slash in error handler

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Checklist

• I have read the contribution guidelines
• Pull request provided for main branch, backports managed with label
• Good housekeeping of code, cleaning up comments, tests, and documentation
• Clean commit history broken into understandable chucks, avoiding big commits with hundreds of files, cautious of reformatting and whitespace changes
• Clean commit messages, longer verbose messages are encouraged
• API Changes are identified in commit messages
• Testing provided for features or enhancements using automatic tests
• User documentation provided for new features or enhancements in manual
• Build documentation provided for development instructions in README.md files
• Library management using pom.xml dependency management. Update build documentation with intended library use and library tutorials or documentation

[CLAassistant]

All committers have signed the CLA.

[wangf1122]

@josegar74 @ianwallen

This is for backporting #8494 and conflict resolving

[josegar74]

@wangf1122 please execute mvn clean install -DskipTests on the root folder, so JS Prettier is executed and commit the reformatted NeedHelpDirective.js

[wangf1122]

@josegar74

Yes, i have rebuilt with maven and the prettier plugin reformatted this js file. Please take a look