Heartbeat API with device token authentication

app/controllers/heartbeats_controller.rb

@@ -0,0 +1,10 @@
+class HeartbeatsController < ApplicationController
+  before_action :authenticate_device
+  respond_to :json
+  
+  def create
+    heartbeat = Heartbeat.create(device: @device)
+    render json: { next_heartbeat_time: heartbeat.next_heartbeat_time }, 
+      status: :created
+  end
+end