treewide: Format all Nix files

Format all Nix files using the officially approved formatter,
making the CI check introduced in the previous commit succeed:

  nix-build ci -A fmt.check

This is the next step of the of the [implementation](https://github.com/NixOS/nixfmt/issues/153)
of the accepted [RFC 166](https://github.com/NixOS/rfcs/pull/166).

This commit will lead to merge conflicts for a number of PRs,
up to an estimated ~1100 (~33%) among the PRs with activity in the past 2
months, but that should be lower than what it would be without the previous
[partial treewide format](https://github.com/NixOS/nixpkgs/pull/322537).

Merge conflicts caused by this commit can now automatically be resolved while rebasing using the
[auto-rebase script](8616af08d9/maintainers/scripts/auto-rebase).

If you run into any problems regarding any of this, please reach out to the
[formatting team](https://nixos.org/community/teams/formatting/) by
pinging @NixOS/nix-formatting.

nixos/modules/services/web-apps/davis.nix

@@ -468,10 +468,13 @@ in
         "davis-env-setup.service"
         "davis-db-migrate.service"
       ];
-      systemd.services.phpfpm-davis.requires = [
-        "davis-env-setup.service"
-        "davis-db-migrate.service"
-      ] ++ lib.optional mysqlLocal "mysql.service" ++ lib.optional pgsqlLocal "postgresql.service";
+      systemd.services.phpfpm-davis.requires =
+        [
+          "davis-env-setup.service"
+          "davis-db-migrate.service"
+        ]
+        ++ lib.optional mysqlLocal "mysql.service"
+        ++ lib.optional pgsqlLocal "postgresql.service";
       systemd.services.phpfpm-davis.serviceConfig.ReadWritePaths = [ cfg.dataDir ];
 
       services.nginx = lib.mkIf (cfg.nginx != null) {