Merge branch 'api-delete-todos' into 'master'

Api delete todos

## What does this MR do?

It changes the `DELETE /todos` to only return the number of marked todos.

## Why was this MR needed?

Before it returned the marked todos as an paginated array. Since we deleted/marked the todos, there was no way to get the rest of the todos.

## What are the relevant issue numbers?

Closes #19678

## Does this MR meet the acceptance criteria?

~~- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added~~
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5341

doc/api/todos.md

@@ -277,8 +277,7 @@ Example Response:
 ## Mark all todos as done
-Marks all pending todos for the current user as done. All todos marked as done
-are returned in the response.
+Marks all pending todos for the current user as done. It returns the number of marked todos.
 ```
 DELETE /todos
@@ -291,154 +290,7 @@ curl -X DELETE -H "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.c
 Example Response:
 ```json
-[
-  {
-    "id": 102,
-    "project": {
-      "id": 2,
-      "name": "Gitlab Ce",
-      "name_with_namespace": "Gitlab Org / Gitlab Ce",
-      "path": "gitlab-ce",
-      "path_with_namespace": "gitlab-org/gitlab-ce"
-    },
-    "author": {
-      "name": "Administrator",
-      "username": "root",
-      "id": 1,
-      "state": "active",
-      "avatar_url": "http://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=80&d=identicon",
-      "web_url": "https://gitlab.example.com/u/root"
-    },
-    "action_name": "marked",
-    "target_type": "MergeRequest",
-    "target": {
-      "id": 34,
-      "iid": 7,
-      "project_id": 2,
-      "title": "Dolores in voluptatem tenetur praesentium omnis repellendus voluptatem quaerat.",
-      "description": "Et ea et omnis illum cupiditate. Dolor aspernatur tenetur ducimus facilis est nihil. Quo esse cupiditate molestiae illo corrupti qui quidem dolor.",
-      "state": "opened",
-      "created_at": "2016-06-17T07:49:24.419Z",
-      "updated_at": "2016-06-17T07:52:43.484Z",
-      "target_branch": "tutorials_git_tricks",
-      "source_branch": "DNSBL_docs",
-      "upvotes": 0,
-      "downvotes": 0,
-      "author": {
-        "name": "Maxie Medhurst",
-        "username": "craig_rutherford",
-        "id": 12,
-        "state": "active",
-        "avatar_url": "http://www.gravatar.com/avatar/a0d477b3ea21970ce6ffcbb817b0b435?s=80&d=identicon",
-        "web_url": "https://gitlab.example.com/u/craig_rutherford"
-      },
-      "assignee": {
-        "name": "Administrator",
-        "username": "root",
-        "id": 1,
-        "state": "active",
-        "avatar_url": "http://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=80&d=identicon",
-        "web_url": "https://gitlab.example.com/u/root"
-      },
-      "source_project_id": 2,
-      "target_project_id": 2,
-      "labels": [],
-      "work_in_progress": false,
-      "milestone": {
-        "id": 32,
-        "iid": 2,
-        "project_id": 2,
-        "title": "v1.0",
-        "description": "Assumenda placeat ea voluptatem voluptate qui.",
-        "state": "active",
-        "created_at": "2016-06-17T07:47:34.163Z",
-        "updated_at": "2016-06-17T07:47:34.163Z",
-        "due_date": null
-      },
-      "merge_when_build_succeeds": false,
-      "merge_status": "cannot_be_merged",
-      "subscribed": true,
-      "user_notes_count": 7
-    },
-    "target_url": "https://gitlab.example.com/gitlab-org/gitlab-ce/merge_requests/7",
-    "body": "Dolores in voluptatem tenetur praesentium omnis repellendus voluptatem quaerat.",
-    "state": "done",
-    "created_at": "2016-06-17T07:52:35.225Z"
-  },
-  {
-    "id": 98,
-    "project": {
-      "id": 2,
-      "name": "Gitlab Ce",
-      "name_with_namespace": "Gitlab Org / Gitlab Ce",
-      "path": "gitlab-ce",
-      "path_with_namespace": "gitlab-org/gitlab-ce"
-    },
-    "author": {
-      "name": "Maxie Medhurst",
-      "username": "craig_rutherford",
-      "id": 12,
-      "state": "active",
-      "avatar_url": "http://www.gravatar.com/avatar/a0d477b3ea21970ce6ffcbb817b0b435?s=80&d=identicon",
-      "web_url": "https://gitlab.example.com/u/craig_rutherford"
-    },
-    "action_name": "assigned",
-    "target_type": "MergeRequest",
-    "target": {
-      "id": 34,
-      "iid": 7,
-      "project_id": 2,
-      "title": "Dolores in voluptatem tenetur praesentium omnis repellendus voluptatem quaerat.",
-      "description": "Et ea et omnis illum cupiditate. Dolor aspernatur tenetur ducimus facilis est nihil. Quo esse cupiditate molestiae illo corrupti qui quidem dolor.",
-      "state": "opened",
-      "created_at": "2016-06-17T07:49:24.419Z",
-      "updated_at": "2016-06-17T07:52:43.484Z",
-      "target_branch": "tutorials_git_tricks",
-      "source_branch": "DNSBL_docs",
-      "upvotes": 0,
-      "downvotes": 0,
-      "author": {
-        "name": "Maxie Medhurst",
-        "username": "craig_rutherford",
-        "id": 12,
-        "state": "active",
-        "avatar_url": "http://www.gravatar.com/avatar/a0d477b3ea21970ce6ffcbb817b0b435?s=80&d=identicon",
-        "web_url": "https://gitlab.example.com/u/craig_rutherford"
-      },
-      "assignee": {
-        "name": "Administrator",
-        "username": "root",
-        "id": 1,
-        "state": "active",
-        "avatar_url": "http://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=80&d=identicon",
-        "web_url": "https://gitlab.example.com/u/root"
-      },
-      "source_project_id": 2,
-      "target_project_id": 2,
-      "labels": [],
-      "work_in_progress": false,
-      "milestone": {
-        "id": 32,
-        "iid": 2,
-        "project_id": 2,
-        "title": "v1.0",
-        "description": "Assumenda placeat ea voluptatem voluptate qui.",
-        "state": "active",
-        "created_at": "2016-06-17T07:47:34.163Z",
-        "updated_at": "2016-06-17T07:47:34.163Z",
-        "due_date": null
-      },
-      "merge_when_build_succeeds": false,
-      "merge_status": "cannot_be_merged",
-      "subscribed": true,
-      "user_notes_count": 7
-    },
-    "target_url": "https://gitlab.example.com/gitlab-org/gitlab-ce/merge_requests/7",
-    "body": "Dolores in voluptatem tenetur praesentium omnis repellendus voluptatem quaerat.",
-    "state": "done",
-    "created_at": "2016-06-17T07:49:24.624Z"
-  },
-]
+3
 ```
 [ce-3188]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3188

lib/api/todos.rb

@@ -75,7 +75,7 @@ module API
         todos = find_todos
         todos.each(&:done)
-        present paginate(Kaminari.paginate_array(todos)), with: Entities::Todo, current_user: current_user
+        todos.length
       end
     end
   end

spec/requests/api/todos_spec.rb

@@ -134,8 +134,7 @@ describe API::Todos, api: true do
         delete api('/todos', john_doe)
         expect(response.status).to eq(200)
-        expect(json_response).to be_an Array
-        expect(json_response.length).to eq(3)
+        expect(response.body).to eq('3')
         expect(pending_1.reload).to be_done
         expect(pending_2.reload).to be_done
         expect(pending_3.reload).to be_done