Direct messages column (#4514)

* Added a timeline for Direct statuses
* Lists all Direct statuses you've sent and received
* Displayed in Getting Started
* Streaming server support for direct TL

* Changes to match other timelines in 2.0

app/controllers/api/v1/timelines/direct_controller.rb

@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+class Api::V1::Timelines::DirectController < Api::BaseController
+  before_action -> { doorkeeper_authorize! :read }, only: [:show]
+  before_action :require_user!, only: [:show]
+  after_action :insert_pagination_headers, unless: -> { @statuses.empty? }
+
+  respond_to :json
+
+  def show
+    @statuses = load_statuses
+    render json: @statuses, each_serializer: REST::StatusSerializer, relationships: StatusRelationshipsPresenter.new(@statuses, current_user&.account_id)
+  end
+
+  private
+
+  def load_statuses
+    cached_direct_statuses
+  end
+
+  def cached_direct_statuses
+    cache_collection direct_statuses, Status
+  end
+
+  def direct_statuses
+    direct_timeline_statuses.paginate_by_max_id(
+      limit_param(DEFAULT_STATUSES_LIMIT),
+      params[:max_id],
+      params[:since_id]
+    )
+  end
+
+  def direct_timeline_statuses
+    Status.as_direct_timeline(current_account)
+  end
+
+  def insert_pagination_headers
+    set_pagination_headers(next_path, prev_path)
+  end
+
+  def pagination_params(core_params)
+    params.permit(:local, :limit).merge(core_params)
+  end
+
+  def next_path
+    api_v1_timelines_direct_url pagination_params(max_id: pagination_max_id)
+  end
+
+  def prev_path
+    api_v1_timelines_direct_url pagination_params(since_id: pagination_since_id)
+  end
+
+  def pagination_max_id
+    @statuses.last.id
+  end
+
+  def pagination_since_id
+    @statuses.first.id
+  end
+end