refactor: migrate is_set method in helper (#1)

plugins/fastlane-plugin-android_cd/lib/fastlane/plugin/android_cd/actions/build_and_deploy.rb

@@ -1,11 +1,7 @@
 require 'fastlane/action'
 require_relative '../helper/android_cd_helper'
 
-def is_set variable
-  str_variable = variable
-  str_variable = variable.strip if variable.class.to_s == "String"
-  variable && !(str_variable.nil? || str_variable.empty?)
-end
+
 
 module Fastlane
   module Actions
@@ -13,7 +9,7 @@ module Fastlane
       def self.run(params)
         
         # Check parameters
-        unless is_set(params[:beta_type])
+        unless Helper::AndroidCdHelper.is_set(params[:beta_type])
           UI.error("Parameters beta_type cannot be null")
           puts "Error on beta type parameter"
         end

plugins/fastlane-plugin-android_cd/lib/fastlane/plugin/android_cd/helper/android_cd_helper.rb

@@ -21,6 +21,12 @@ module Fastlane
           puts "Erreur lors de la décompression du fichier GPG"
         end
       end
+
+      def self.is_set variable
+        str_variable = variable
+        str_variable = variable.strip if variable.class.to_s == "String"
+        variable && !(str_variable.nil? || str_variable.empty?)
+      end
     end
   end
 end