Use licensee methods

Prior to this change, there were still usages of
licensee[:ATTRIBUTE_NAME] although there were methods introduced to make
the access easier. This change will use those methods in the necessary
places.

ee/app/models/license.rb

@@ -360,7 +360,7 @@ class License < ApplicationRecord
   end
 
   def data_filename
-    company_name = self.licensee["Company"] || self.licensee.each_value.first
+    company_name = self.licensee_company || self.licensee.each_value.first
     clean_company_name = company_name.gsub(/[^A-Za-z0-9]/, "")
     "#{clean_company_name}.gitlab-license"
   end

ee/app/services/historical_user_data/csv_service.rb

@@ -34,10 +34,10 @@ module HistoricalUserData
     def header_csv
       CSV.generate do |csv|
         csv << ['License Key', license.data]
-        csv << ['Email', license.licensee['Email']]
+        csv << ['Email', license.licensee_email]
         csv << ['License Start Date', license.starts_at&.to_s(:csv)]
         csv << ['License End Date', license.expires_at&.to_s(:csv)]
-        csv << ['Company', license.licensee['Company']]
+        csv << ['Company', license.licensee_company]
         csv << ['Generated At', Time.current.to_s(:csv)]
         csv << ['']
       end

ee/app/views/admin/licenses/_summary.html.haml

@@ -11,7 +11,7 @@
           = render 'admin/licenses/license_status'
         %span.gl-ml-5
           = _('Licensed to:')
-          %strong= @license.licensee['Name']
-          = "(#{@license.licensee['Email']})"
+          %strong= @license.licensee_name
+          = "(#{@license.licensee_email})"
     %div
       = link_to 'View details', admin_license_path, class: "gl-button btn btn-default"

ee/app/workers/active_user_count_threshold_worker.rb

@@ -21,7 +21,7 @@ class ActiveUserCountThresholdWorker # rubocop:disable Scalability/IdempotentWor
         .to_set
       # rubocop:enable CodeReuse/ActiveRecord
 
-      recipients << license.licensee["Email"] if license.licensee["Email"]
+      recipients << license.licensee_email if license.licensee_email
 
       LicenseMailer.approaching_active_user_count_limit(recipients.to_a)
     end