nixos/nextcloud: fix `nginx`-config for Nextcloud 19 and older

It seems as I misconfigured `nginx` for certain cases such as the
`ldap`-plugin[1] in 42f6244899. This patch
fixes the `nginx`-config to match the upstream recommendations[2].

Also added a comment to the module to remind myself to ensure that
`nginx` will work with both v19 and v20 as soon as the latter is
released and can be packaged in `nixpkgs`.

Co-authored-by: nivadis <nivadis@users.noreply.github.com>

[1] https://github.com/nextcloud/server/issues/16194#issuecomment-688839888
[2] https://docs.nextcloud.com/server/19/admin_manual/installation/nginx.html

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

@@ -542,6 +542,9 @@ in {
       environment.systemPackages = [ occ ];
 
       services.nginx.enable = mkDefault true;
+
+      # FIXME(ma27) make sure that the config works fine with Nextcloud 19
+      # *and* Nextcloud 20 as soon as it gets released.
       services.nginx.virtualHosts.${cfg.hostName} = {
         root = cfg.package;
         locations = {
@@ -555,7 +558,7 @@ in {
           };
           "/" = {
             priority = 900;
-            extraConfig = "try_files $uri $uri/ /index.php$request_uri;";
+            extraConfig = "rewrite ^ /index.php;";
           };
           "~ ^/store-apps" = {
             priority = 201;
@@ -579,7 +582,7 @@ in {
           "~ ^/(?:\\.|autotest|occ|issue|indie|db_|console)".extraConfig = ''
             return 404;
           '';
-          "~ \\.php(?:$|/)" = {
+          "~ ^\\/(?:index|remote|public|cron|core\\/ajax\\/update|status|ocs\\/v[12]|updater\\/.+|oc[ms]-provider\\/.+|.+\\/richdocumentscode\\/proxy)\\.php(?:$|\\/)" = {
             priority = 500;
             extraConfig = ''
               include ${config.services.nginx.package}/conf/fastcgi.conf;