REFACTOR: fix code review comments

- omit action_id and target_id
- follow api to use String type for action param
- update todo api doc
- rspec rewording

doc/api/todos.md

@@ -21,12 +21,12 @@ Parameters:
 
 | Attribute | Type | Required | Description |
 | --------- | ---- | -------- | ----------- |
-| `action` | string | no | The action to be filtered. Can be `assigned`, `mentioned`, `build_failed`, `marked`, `approval_required`, `unmergeable` or `directly_addressed`. |
+| `action` | string | no | The action to be filtered. Can be `assigned`, `mentioned`, `build_failed`, `marked`, `approval_required`, `unmergeable`, `directly_addressed` or `merge_train_removed`. |
 | `author_id` | integer | no | The ID of an author |
 | `project_id` | integer | no | The ID of a project |
 | `group_id` | integer | no | The ID of a group |
 | `state` | string | no | The state of the todo. Can be either `pending` or `done` |
-| `type` | string | no | The type of a todo. Can be either `Issue` or `MergeRequest` |
+| `type` | string | no | The type of a todo. Can be either `Issue`, `MergeRequest`, `DesignManagement::Design` or `AlertManagement::Alert` |
 
 ```shell
 curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/todos"

lib/api/todos.rb

@@ -40,11 +40,9 @@ module API
     resource :todos do
       helpers do
         params :todo_filters do
-          optional :action_id, Integer
-          optional :action, Array[String], values: Todo::ACTION_NAMES.values.map(&:to_s)
+          optional :action, String, values: Todo::ACTION_NAMES.values.map(&:to_s)
           optional :author_id, Integer
           optional :state, String, values: Todo.state_machine.states.map(&:name).map(&:to_s)
-          optional :target_id, Integer
           optional :type, Array[String], values: TodosFinder.todo_types
           optional :project_id, Integer
           optional :group_id, Integer

spec/requests/api/todos_spec.rb

@@ -36,7 +36,7 @@ RSpec.describe API::Todos do
     context 'when authenticated' do
       context 'when invalid params' do
         context "invalid action" do
-          it 'returns argument error' do
+          it 'returns 400' do
             get api('/todos', john_doe), params: { action: 'InvalidAction' }
             expect(response).to have_gitlab_http_status(:bad_request)
           end