Add optional query param in _field_caps to return only fields with value in index (#2413)

Author: piergm

output/openapi/elasticsearch-serverless-openapi.json

@@ -75,6 +75,13 @@ export interface Request extends RequestBase {
      * @availability serverless
      */
     types?: string[]
+    /**
+     * If false, empty fields are not included in the response.
+     * @availability stack since=8.13.0
+     * @availability serverless
+     * @server_default true
+     */
+    include_empty_fields?: boolean
   }
   body: {
     /**

output/schema/schema.json

@@ -59,6 +59,11 @@
       "types": {
         "type": "list",
         "description": "Only return results for fields that have one of the types in the list"
+      },
+      "include_empty_fields": {
+        "type": "boolean",
+        "default": true,
+        "description": "Indicates whether empty fields should be included in the response."
       }
     },
     "body": {