Add nested groups to the API

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

changelogs/unreleased/dz-nested-groups-api.yml

+---
+title: Add nested groups to the API
+merge_request: 9034
+author:

doc/api/groups.md

@@ -32,7 +32,8 @@ GET /groups
     "web_url": "http://localhost:3000/groups/foo-bar",
     "request_access_enabled": false,
     "full_name": "Foobar Group",
-    "full_path": "foo-bar"
+    "full_path": "foo-bar",
+    "parent_id": null
   }
 ]
 ```
@@ -156,8 +157,9 @@ Example response:
   "avatar_url": null,
   "web_url": "https://gitlab.example.com/groups/twitter",
   "request_access_enabled": false,
-  "full_name": "Foobar Group",
-  "full_path": "foo-bar",
+  "full_name": "Twitter",
+  "full_path": "twitter",
+  "parent_id": null,
   "projects": [
     {
       "id": 7,
@@ -332,6 +334,7 @@ Parameters:
 - `visibility_level` (optional) - The group's visibility. 0 for private, 10 for internal, 20 for public.
 - `lfs_enabled` (optional)      - Enable/disable Large File Storage (LFS) for the projects in this group
 - `request_access_enabled` (optional) - Allow users to request member access.
+- `parent_id` (optional) - The parent group id for creating nested group.
 ## Transfer project to group
@@ -383,6 +386,7 @@ Example response:
   "request_access_enabled": false,
   "full_name": "Foobar Group",
   "full_path": "foo-bar",
+  "parent_id": null,
   "projects": [
     {
       "id": 9,

lib/api/entities.rb

@@ -138,6 +138,7 @@ module API
       expose :web_url
       expose :request_access_enabled
       expose :full_name, :full_path
+      expose :parent_id
       expose :statistics, if: :statistics do
         with_options format_with: -> (value) { value.to_i } do

lib/api/groups.rb

@@ -73,6 +73,7 @@ module API
       params do
         requires :name, type: String, desc: 'The name of the group'
         requires :path, type: String, desc: 'The path of the group'
+        optional :parent_id, type: Integer, desc: 'The parent group id for creating nested group'
         use :optional_params
       end
       post do

spec/requests/api/groups_spec.rb

@@ -179,6 +179,7 @@ describe API::Groups, api: true  do
         expect(json_response['request_access_enabled']).to eq(group1.request_access_enabled)
         expect(json_response['full_name']).to eq(group1.full_name)
         expect(json_response['full_path']).to eq(group1.full_path)
+        expect(json_response['parent_id']).to eq(group1.parent_id)
         expect(json_response['projects']).to be_an Array
         expect(json_response['projects'].length).to eq(2)
         expect(json_response['shared_projects']).to be_an Array
@@ -398,6 +399,19 @@ describe API::Groups, api: true  do
         expect(json_response["request_access_enabled"]).to eq(group[:request_access_enabled])
       end
+      it "creates a nested group" do
+        parent = create(:group)
+        parent.add_owner(user3)
+        group = attributes_for(:group, { parent_id: parent.id })
+
+        post api("/groups", user3), group
+
+        expect(response).to have_http_status(201)
+
+        expect(json_response["full_path"]).to eq("#{parent.path}/#{group[:path]}")
+        expect(json_response["parent_id"]).to eq(parent.id)
+      end
+
       it "does not create group, duplicate" do
         post api("/groups", user3), { name: 'Duplicate Test', path: group2.path }