[Rollup] Specialize validation exception for easier management (#30339)

Extends ActionRequestValidationException with a rollup-specific version
to make it easier to handle mapping validation issues on the client
side.

The type will now be `rollup_action_request_validation_exception`
instead of `action_request_validation_exception`

Author: polyfractal

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/PutRollupJobAction.java

@@ -82,8 +82,8 @@ public ActionRequestValidationException validate() {
             return null;
         }
 
-        public ActionRequestValidationException validateMappings(Map<String, Map<String, FieldCapabilities>> fieldCapsResponse) {
-            ActionRequestValidationException validationException = new ActionRequestValidationException();
+        public RollupActionRequestValidationException validateMappings(Map<String, Map<String, FieldCapabilities>> fieldCapsResponse) {
+            RollupActionRequestValidationException validationException = new RollupActionRequestValidationException();
             if (fieldCapsResponse.size() == 0) {
                 validationException.addValidationError("Could not find any fields in the index/index-pattern that were configured in job");
                 return validationException;

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/RollupActionRequestValidationException.java

@@ -0,0 +1,11 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.core.rollup.action;
+
+import org.elasticsearch.action.ActionRequestValidationException;
+
+public class RollupActionRequestValidationException extends ActionRequestValidationException {
+}

x-pack/plugin/src/test/resources/rest-api-spec/test/rollup/put_job.yml

@@ -159,5 +159,33 @@ setup:
             ]
           }
 
+---
+"Validation failures":
+
+  - do:
+      catch: /Could not find a \[numeric\] field with name \[field_doesnt_exist\] in any of the indices matching the index pattern/
+      headers:
+        Authorization: "Basic eF9wYWNrX3Jlc3RfdXNlcjp4LXBhY2stdGVzdC1wYXNzd29yZA==" # run as x_pack_rest_user, i.e. the test setup superuser
+      xpack.rollup.put_job:
+        id: foo
+        body:  >
+          {
+            "index_pattern": "foo",
+            "rollup_index": "foo_rollup",
+            "cron": "*/30 * * * * ?",
+            "page_size" :10,
+            "groups" : {
+              "date_histogram": {
+                "field": "the_field",
+                "interval": "1h"
+              }
+            },
+            "metrics": [
+              {
+                "field": "field_doesnt_exist",
+                "metrics": ["min", "max", "sum"]
+              }
+            ]
+          }