[8.14] [Inventory/Metric/Custom threshold] Specify fields instead of …

…'*' in fieldCaps request (elastic#184968) (elastic#185010)

# Backport

This will backport the following commits from `main` to `8.14`:
- [[Inventory/Metric/Custom threshold] Specify fields instead of '*' in
fieldCaps request
(elastic#184968)](elastic#184968)

<!--- Backport version: 8.9.8 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Bena
Kansara","email":"69037875+benakansara@users.noreply.github.com"},"sourceCommit":{"committedDate":"2024-06-07T13:39:37Z","message":"[Inventory/Metric/Custom
threshold] Specify fields instead of '*' in fieldCaps request
(elastic#184968)\n\nResolves
elastic#184909
threshold] Specify fields instead of '*' in fieldCaps request
(elastic#184968)\n\nResolves
elastic#184909
threshold] Specify fields instead of '*' in fieldCaps request
(elastic#184968)\n\nResolves
elastic#184909"}]}]
BACKPORT-->

x-pack/plugins/observability_solution/infra/server/lib/alerting/common/utils.ts

@@ -195,7 +195,7 @@ export const doFieldsExist = async (
   // Get all supported fields
   const respMapping = await esClient.fieldCaps({
     index,
-    fields: '*',
+    fields,
   });
 
   const fieldsExisted: Record<string, boolean> = {};

x-pack/plugins/observability_solution/observability/server/lib/rules/custom_threshold/utils.ts

@@ -130,7 +130,7 @@ export const doFieldsExist = async (
   // Get all supported fields
   const respMapping = await esClient.fieldCaps({
     index,
-    fields: '*',
+    fields,
   });
 
   const fieldsExisted: Record<string, boolean> = {};