Add REST API for Web Push Notifications subscriptions (#7445)

- POST /api/v1/push/subscription
- PUT /api/v1/push/subscription
- DELETE /api/v1/push/subscription
- New OAuth scope: "push" (required for the above methods)

app/controllers/api/v1/push/subscriptions_controller.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+class Api::V1::Push::SubscriptionsController < Api::BaseController
+  before_action -> { doorkeeper_authorize! :push }
+  before_action :require_user!
+  before_action :set_web_push_subscription
+
+  def create
+    @web_subscription&.destroy!
+
+    @web_subscription = ::Web::PushSubscription.create!(
+      endpoint: subscription_params[:endpoint],
+      key_p256dh: subscription_params[:keys][:p256dh],
+      key_auth: subscription_params[:keys][:auth],
+      data: data_params,
+      user_id: current_user.id,
+      access_token_id: doorkeeper_token.id
+    )
+
+    render json: @web_subscription, serializer: REST::WebPushSubscriptionSerializer
+  end
+
+  def update
+    raise ActiveRecord::RecordNotFound if @web_subscription.nil?
+
+    @web_subscription.update!(data: data_params)
+
+    render json: @web_subscription, serializer: REST::WebPushSubscriptionSerializer
+  end
+
+  def destroy
+    @web_subscription&.destroy!
+    render_empty
+  end
+
+  private
+
+  def set_web_push_subscription
+    @web_subscription = ::Web::PushSubscription.find_by(access_token_id: doorkeeper_token.id)
+  end
+
+  def subscription_params
+    params.require(:subscription).permit(:endpoint, keys: [:auth, :p256dh])
+  end
+
+  def data_params
+    return {} if params[:data].blank?
+    params.require(:data).permit(alerts: [:follow, :favourite, :reblog, :mention])
+  end
+end