create fcm legacy http protocol client

Author: Roy-Mao

lib/fcm/client.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require 'fcm/connection'
+require 'fcm/response'
+require 'fcm/client/notification_delivery'
+require 'fcm/client/notification_setting'
+require 'fcm/client/instance_topic_management'
+
+module Fcm
+  # Fcm Client class for legacy http protocol API connections
+  #
+  # @see https://firebase.google.com/docs/cloud-messaging/http-server-ref
+  class Client
+    include Fcm::Connection
+    include Fcm::Response
+    include Fcm::Client::NotificationDilivery
+    include Fcm::Client::NotificationSetting
+    include Fcm::Client::InstanceTopicManagement
+
+    # @see https://firebase.google.com/docs/projects/api-keys
+    # @param api_key [String] Firebase API key
+    # @return [Client] client instance
+    def initialize(api_key)
+      @api_key = api_key
+    end
+
+    private
+
+    def authorization_headers
+      {
+        'Content-Type' => 'application/json',
+        'Authorization' => "key=#{@api_key}"
+      }
+    end
+  end
+end