modules/nextcloud: PHP's session gc should match

nextcloud session_lifetime.

Use webp as preview format.

Use NixOS default of 1s for opcache revalidation for quicker
updates after PHP code changes.

Enable debug logging to track down issues with Nextcloud
sessions.

modules/nextcloud/default.nix

@@ -127,11 +127,12 @@
         "opcache.interned_strings_buffer" = "32";
         "opcache.max_accelerated_files" = "16229";
         "opcache.memory_consumption" = "256";
-        # https://docs.nextcloud.com/server/latest/admin_manual/installation/server_tuning.html#enable-php-opcache
-        "opcache.revalidate_freq" = "60";
         # https://docs.nextcloud.com/server/latest/admin_manual/installation/server_tuning.html#:~:text=opcache.jit%20%3D%201255%20opcache.jit_buffer_size%20%3D%20128m
         "opcache.jit" = "1255";
         "opcache.jit_buffer_size" = "128M";
+        # Ensure that this matches nextcloud's session_lifetime config
+        # https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/config_sample_php_parameters.html#session-lifetime
+        "session.gc_maxlifetime" = "86400";
       };
 
       # Calculated with 4GiB RAM, 80MiB process size available on

modules/nextcloud/preview-generation.nix

@@ -41,6 +41,7 @@
         preview_max_memory = 512; # MB
         preview_max_x = 2048; # px
         preview_max_y = 2048; # px
+        preview_format = "webp";
         preview_max_scale_factor = 1;
         "preview_ffmpeg_path" = lib.getExe pkgs.ffmpeg-headless;
       };