Move _meta section back inside mappings, in legacy templates. (elastic#1186)

This fixes an issue introduced by elastic#1156, discovered in elastic#1180. Composable templates support `_meta` at the template's root, but legacy templates don't. So we're just putting it back inside the mappings for legacy templates.

This also fixes missing updates to the component template, after the introduction of wildcard in elastic#1098.

Author: Mathieu Martin

CHANGELOG.next.md

@@ -30,7 +30,7 @@ Thanks, you're awesome :-) -->
 
 #### Added
 
-* Added component templates for ECS field sets. #1156
+* Added component templates for ECS field sets. #1156, #1186
 
 #### Improvements
 

experimental/generated/elasticsearch/7/template.json

@@ -1,11 +1,11 @@
 {
-  "_meta": {
-    "version": "1.7.0+exp"
-  },
   "index_patterns": [
     "try-ecs-*"
   ],
   "mappings": {
+    "_meta": {
+      "version": "1.7.0+exp"
+    },
     "date_detection": false,
     "dynamic_templates": [
       {

generated/elasticsearch/6/template.json

@@ -1,12 +1,12 @@
 {
-  "_meta": {
-    "version": "1.7.0"
-  },
   "index_patterns": [
     "try-ecs-*"
   ],
   "mappings": {
     "_doc": {
+      "_meta": {
+        "version": "1.7.0"
+      },
       "date_detection": false,
       "dynamic_templates": [
         {

generated/elasticsearch/7/template.json

@@ -1,11 +1,11 @@
 {
-  "_meta": {
-    "version": "1.7.0"
-  },
   "index_patterns": [
     "try-ecs-*"
   ],
   "mappings": {
+    "_meta": {
+      "version": "1.7.0"
+    },
     "date_detection": false,
     "dynamic_templates": [
       {

scripts/generators/es_template.py

@@ -184,10 +184,15 @@ def template_settings(es_version, ecs_version, mappings_section, template_settin
             template = json.load(f)
     else:
         template = default_template_settings(ecs_version)
+
     if es_version == 6:
         template['mappings'] = {'_doc': mappings_section}
     else:
         template['mappings'] = mappings_section
+
+    # _meta can't be at template root in legacy templates, so moving back to mappings section
+    mappings_section['_meta'] = template.pop('_meta')
+
     return template