nixos/release-notes: deprecate services.pdns-recursor.settings

Author: rnhmjoj

nixos/doc/manual/release-notes/rl-2505.section.md

@@ -267,6 +267,13 @@
   [not recommended by upstream](https://docs.nextcloud.com/server/30/admin_manual/installation/system_requirements.html)
   and thus doesn't qualify as default.
 
+- PowerDNS Recursor has been updated to version 5.1.2, which comes with a new YAML configuration format (`recursor.yml`)
+  and deprecates the previous format (`recursor.conf`). Accordingly, the NixOS option `services.pdns-recursor.settings`
+  has been renamed to [old-settings](#opt-services.pdns-recursor.old-settings) and will be provided for backward compatibility
+  until the next NixOS release. Users are asked to migrate their settings to the new [yaml-settings](#opt-services.pdns-recursor.old-settings)
+  option following this [guide](https://doc.powerdns.com/recursor/appendices/yamlconversion.html).
+  Note that options other than `services.pdns-recursor.settings` are unaffacted by this change.
+
 - Nextcloud's default FPM pool settings have been increased according to upstream recommentations. It's advised
   to review the new defaults and description of
   [](#opt-services.nextcloud.poolSettings).