Specify which fields are allowed to be nested (#33)

Author: felixbarny

spec/spec.json

@@ -15,7 +15,15 @@
             "type": "string",
             "required": true,
             "index": 1,
-            "url": "https://www.elastic.co/guide/en/ecs/current/ecs-log.html"
+            "top_level_field": true,
+            "url": "https://www.elastic.co/guide/en/ecs/current/ecs-log.html",
+            "comment": [
+                "This field SHOULD NOT be a nested object field but at the top level with a dot in the property name.",
+                "This is to make the JSON logs more human-readable.",
+                "Loggers MAY indent the log level so that the `message` field always starts at the exact same offset,",
+                "no matter the number of characters the log level has.",
+                "For example: `'DEBUG'` (5 chars) will not be indented, whereas ` 'WARN'` (4 chars) will be indented by one space character."
+            ]
         },
         "message": {
             "type": "string",