services.logstash: update example and default filter

nixos/modules/services/logging/logstash.nix

@@ -77,7 +77,7 @@ in
 
       inputConfig = mkOption {
         type = types.lines;
-        default = ''stdin { type => "example" }'';
+        default = ''generator { }'';
         description = "Logstash input configuration.";
         example = ''
           # Read from journal
@@ -90,7 +90,7 @@ in
 
       filterConfig = mkOption {
         type = types.lines;
-        default = ''noop {}'';
+        default = "";
         description = "logstash filter configuration.";
         example = ''
           if [type] == "syslog" {
@@ -108,11 +108,11 @@ in
 
       outputConfig = mkOption {
         type = types.lines;
-        default = ''stdout { debug => true debug_format => "json"}'';
+        default = ''stdout { codec => rubydebug }'';
         description = "Logstash output configuration.";
         example = ''
-          redis { host => "localhost" data_type => "list" key => "logstash" codec => json }
-          elasticsearch { embedded => true }
+          redis { host => ["localhost"] data_type => "list" key => "logstash" codec => json }
+          elasticsearch { }
         '';
       };