user_groups: Include group_id in success response on group creation.

Previously, the `group_id` was not returned in the success
response of the user group creation API.

This commit updates the API to return a success response
containing the unique ID of the user group with the key
`group_id`. This enhancement allows clients to easily reference
the newly created user group.

Fixes: #29686

api_docs/changelog.md

@@ -20,6 +20,13 @@ format used by the Zulip server that they are interacting with.
 
 ## Changes in Zulip 10.0
 
+**Feature level 317**
+
+* [`POST /user_groups/create`](/api/create-user-group):
+  Added `group_id` to the success response of the user group creation
+  endpoint, enabling clients to easily access the unique identifier
+  of the newly created user group.
+
 **Feature level 316**
 
 * `PATCH /realm`, [`GET /events`](/api/get-events),

version.py

@@ -34,7 +34,7 @@ DESKTOP_WARNING_VERSION = "5.9.3"
 # new level means in api_docs/changelog.md, as well as "**Changes**"
 # entries in the endpoint's documentation in `zulip.yaml`.
 
-API_FEATURE_LEVEL = 316  # Last bumped for `can_move_messages_between_topics_group`
+API_FEATURE_LEVEL = 317  # Last bumped for inclusion of `group_id` in user group creation response.
 
 # Bump the minor PROVISION_VERSION to indicate that folks should provision
 # only when going from an old version of the code to a newer version. Bump

zerver/openapi/zulip.yaml

@@ -20457,7 +20457,30 @@ paths:
                 contentType: application/json
       responses:
         "200":
-          $ref: "#/components/responses/SimpleSuccess"
+          description: |
+            A success response containing the unique ID of the user group.
+            This field provides a straightforward way to reference the
+            newly created user group.
+
+            **Changes**: New in Zulip 10.0 (feature level 317).
+          content:
+            application/json:
+              schema:
+                allOf:
+                  - $ref: "#/components/schemas/JsonSuccessBase"
+                  - required:
+                      - group_id
+                    additionalProperties: false
+                    properties:
+                      result: {}
+                      msg: {}
+                      ignored_parameters_unsupported: {}
+                      group_id:
+                        type: integer
+                        description: |
+                          The unique ID of the created user group.
+                    example: {"msg": "", "result": "success", "group_id": 123}
+
         "400":
           description: Bad request.
           content:

zerver/views/user_groups.py

@@ -101,8 +101,7 @@ def add_user_group(
             add_subgroups_to_user_group(
                 context.supergroup, context.direct_subgroups, acting_user=user_profile
             )
-
-    return json_success(request)
+    return json_success(request, data={"group_id": user_group.id})
 
 
 @require_member_or_admin