Add OpenAPI specification for bulk_get saved object APIs (#6860)

* Add OpenAPI specification for bulk_get saved object APIs

Signed-off-by: Yuanqi(Ella) Zhu <[email protected]>

* Changeset file for PR #6860 created/updated

* Apply suggestions from code review

Co-authored-by: Lu Yu <[email protected]>
Signed-off-by: Yuanqi(Ella) Zhu <[email protected]>

---------

Signed-off-by: Yuanqi(Ella) Zhu <[email protected]>
Signed-off-by: Yuanqi(Ella) Zhu <[email protected]>
Co-authored-by: opensearch-changeset-bot[bot] <154024398+opensearch-changeset-bot[bot]@users.noreply.github.com>
Co-authored-by: Lu Yu <[email protected]>
(cherry picked from commit 6b2db4d)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

changelogs/fragments/6860.yml

@@ -0,0 +1,2 @@
+doc:
+- Add OpenAPI specification for bulk_get saved object APIs ([#6860](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/6860))

docs/openapi/saved_objects/saved_objects.yml

@@ -126,7 +126,7 @@ paths:
           example: 1
         - in: query
           name: search
-          description: The search query that filters the saved objects.
+          description: The simple_query_string query that filters the objects in the response.
           schema:
             type: string
           example: "open*"
@@ -355,6 +355,38 @@ paths:
             application/json:
               schema:
                 type: object
+  /api/saved_objects/_bulk_get:
+    get:
+      tags:
+        - saved objects
+      summary: Bulk get saved objects
+      requestBody:
+        required: true
+        description: Array of criteria including id, type, fields used to retrieve matching saved objects
+        content: 
+          application/json:
+            schema:
+              type: array
+              items:
+                type: object
+                properties:
+                  id:
+                    type: string
+                    required: true
+                    description: Unique id of the saved object.
+                  type:
+                    type: string
+                    required: true
+                    description: The type of saved object.
+                  fields:
+                    type: array
+                    items:
+                      type: string
+                    description: The fields to return in the attributes key of the object response.
+              example:
+                - id: 67a9021c-c97e-4499-8150-9722ab44edd4
+                  type: visualization
+                  fields: ['title', 'fieldFormatMap']
 components:
   parameters:
     type: