Templates: GET templates doesn't honor the `flat_settings` parameter.

Close #6671

rest-api-spec/test/indices.get_template/10_basic.yaml

@@ -16,7 +16,8 @@ setup:
         name: test
 
   - match: {test.template: "test-*"}
-  - match: {test.settings: {index.number_of_shards: '1', index.number_of_replicas: '0'}}
+  - match: {test.settings: {index: {number_of_shards: '1', number_of_replicas: '0'}}}
+
 ---
 "Get all templates":
 
@@ -43,3 +44,13 @@ setup:
         local: true
 
   - is_true: test
+
+---
+"Get template with flat settings":
+
+  - do:
+      indices.get_template:
+        name: test
+        flat_settings: true
+
+  - match: {test.settings: {index.number_of_shards: '1', index.number_of_replicas: '0'}}

rest-api-spec/test/indices.put_template/10_basic.yaml

@@ -12,6 +12,7 @@
   - do:
       indices.get_template:
         name: test
+        flat_settings: true
 
   - match: {test.template: "test-*"}
   - match: {test.settings: {index.number_of_shards: '1', index.number_of_replicas: '0'}}
@@ -54,6 +55,7 @@
   - do:
       indices.get_template:
         name: test
+        flat_settings: true
 
   - match: {test.template: "test-*"}
   - match: {test.settings: {index.number_of_shards: '1', index.number_of_replicas: '0'}}

src/main/java/org/elasticsearch/cluster/metadata/IndexTemplateMetaData.java

@@ -275,9 +275,7 @@ public class IndexTemplateMetaData {
             builder.field("template", indexTemplateMetaData.template());
 
             builder.startObject("settings");
-            for (Map.Entry<String, String> entry : indexTemplateMetaData.settings().getAsMap().entrySet()) {
-                builder.field(entry.getKey(), entry.getValue());
-            }
+            indexTemplateMetaData.settings().toXContent(builder, params);
             builder.endObject();
 
             if (params.paramAsBoolean("reduce_mappings", false)) {