nixos/postgresql: use postgres 13 for 21.11 (#131018)

Co-authored-by: Kim Lindberger <kim.lindberger@gmail.com>

nixos/doc/manual/from_md/release-notes/rl-2111.section.xml

@@ -32,6 +32,11 @@
           from Python 3.8.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          PostgreSQL now defaults to major version 13.
+        </para>
+      </listitem>
     </itemizedlist>
   </section>
   <section xml:id="sec-release-21.11-new-services">

nixos/doc/manual/release-notes/rl-2111.section.md

@@ -11,6 +11,8 @@ In addition to numerous new and upgraded packages, this release has the followin
 
 - `python3` now defaults to Python 3.9, updated from Python 3.8.
 
+- PostgreSQL now defaults to major version 13.
+
 ## New Services {#sec-release-21.11-new-services}
 
 - [btrbk](https://digint.ch/btrbk/index.html), a backup tool for btrfs subvolumes, taking advantage of btrfs specific capabilities to create atomic snapshots and transfer them incrementally to your backup locations. Available as [services.btrbk](options.html#opt-services.brtbk.instances).

nixos/modules/services/databases/postgresql.nix

@@ -293,7 +293,8 @@ in
       # Note: when changing the default, make it conditional on
       # ‘system.stateVersion’ to maintain compatibility with existing
       # systems!
-      mkDefault (if versionAtLeast config.system.stateVersion "20.03" then pkgs.postgresql_11
+      mkDefault (if versionAtLeast config.system.stateVersion "21.11" then pkgs.postgresql_13
+            else if versionAtLeast config.system.stateVersion "20.03" then pkgs.postgresql_11
             else if versionAtLeast config.system.stateVersion "17.09" then pkgs.postgresql_9_6
             else throw "postgresql_9_5 was removed, please upgrade your postgresql version.");