feat(crawler): update to new user-agent format

crawler/VERSION

@@ -0,0 +1 @@
+2.6.5

crawler/algolia.rb

@@ -1,7 +1,10 @@
 require 'algoliasearch'
 require './config.rb'
+require './user_agent.rb'
 
 Algolia.init(
   application_id: CONFIG['algolia_app_id'],
   api_key: CONFIG['algolia_api_key']
 )
+
+Algolia.set_extra_header 'User-Agent', UserAgent.to_s

crawler/user_agent.rb

@@ -0,0 +1,25 @@
+require 'algoliasearch'
+
+class UserAgent
+  class Version
+    def self.crawler
+      File.read('VERSION').strip
+    end
+
+    def self.client
+      Algolia::VERSION
+    end
+
+    def self.ruby
+      RUBY_VERSION
+    end
+  end
+
+  def self.to_s
+    [
+      "Zendesk Integration (#{Version.crawler})",
+      "Algolia for Ruby (#{Version.client})",
+      "Ruby (#{Version.ruby})"
+    ].join('; ')
+  end
+end