grocy: clear viewcache before start

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

@@ -130,6 +130,16 @@ in {
       };
     };
 
+    # After an update of grocy, the viewcache needs to be deleted. Otherwise grocy will not work
+    # https://github.com/grocy/grocy#how-to-update
+    systemd.services.grocy-setup = {
+      wantedBy = [ "multi-user.target" ];
+      before = [ "phpfpm-grocy.service" ];
+      script = ''
+        rm -rf ${cfg.dataDir}/viewcache/*
+      '';
+    };
+
     services.nginx = {
       enable = true;
       virtualHosts."${cfg.hostName}" = mkMerge [