Setup warning and error documentation links (usefulness)

Thanks for helping improve our documentation!

• There is always room for improvement!
• All contributions (changes and change ideas) - from the largest to the tiniest - help make Nextcloud better and easier to use!

The documentation links in the various setup warnings should be audited to make sure they land in useful spots and that the section they link to documents the stated parameter/situation. Here's a WIP list that I (or anyone) can revise (if they don't have the time to specifically address the matter immediately but want to note it for future follow-up):

• The PHP OPcache module is not properly configured. The OPcache interned strings buffer is nearly full. To assure that repeating strings can be effectively cached, it is recommended to apply “opcache.interned_strings_buffer” to your PHP configuration with a value higher than “32”… For more details see the documentation ↗️
  • Reasonable section to link to, but this parameter (opcache.interned_strings_buffer) isn't discussed here at all or anywhere else in the manual currently (other than offhandedly in the OpenBSD installation chapter)
  • Resources
    • https://help.nextcloud.com/t/solved-opcache-module-not-properly-configured/175941/5
    • https://help.nextcloud.com/t/nextcloud-23-02-opcache-interned-strings-buffer/134007/5 (thanks @MichaIng!)
    • The original PRs

Notes

• Please be patient: this is a large open source project that is overseen by a mixture of volunteers and non-volunteers which are all ultimately busy.
• If your suggestion is a troubleshooting scenario or one you're not 100% certain about, please post for feedback on the Nextcloud Help Forum first.
  • Then return here to bring back your experience to help improve the documentation for clarity, etc. (and link back to the forum discussion in your report!)

Protip: If you want to help move things along (or just help out in other ways too) here are some suggestions:

• Look for areas where you can assist - even seemingly unrelated areas - because doing so frees up resources for your favorite topics and ideas.
• Submit a proposed change - that attempts to addresses your issue - as a pull request.
• Participate in a discussion on some other unresolved submitted idea ("issues") to help move it along.
• Post a comment or review on someone else's proposed change ("pull request") to help move it along.

Start by auditing the setup-warning link for the PHP OPcache interned strings buffer, then compare the linked admin-php-opcache section with the existing mention in the OpenBSD installation chapter. Review the listed resources and original PRs; done means the warning lands on a useful section that documents the stated parameter or situation.