refactor: convert instance validation methods to class methods in Contact class

lab2/contact.rb

@@ -29,23 +29,18 @@ class Contact
     'No contact available'
   end
 
-  private
-
-  def valid_phone_number?(phone)
+  def self.valid_phone_number?(phone)
     /\A\+?[0-9]{9,15}\z/.match?(phone)
   end
 
-  # self
-  def valid_telegram?(telegram)
+  def self.valid_telegram?(telegram)
     /\A@[A-Za-z0-9_]{5,32}\z/.match?(telegram)
   end
 
-  def valid_email?(email)
+  def self.valid_email?(email)
     /\A[^@\s]+@[^@\s]+\.[^@\s]+\z/.match?(email)
   end
 
-  public
-
   def self.new_from_info(info_string)
     info_string = info_string.sub(/^Contact: /, '').strip