Refactor domain admin contact validation logic

- Remove validate_admin_contact_type validation
- Extract age calculation logic into separate methods
- Add helper methods for Estonian ID and birthday age checks
- Improve code organization and readability
- Split complex require_admin_contacts? method into smaller methods

app/models/domain.rb

@@ -206,8 +206,6 @@ class Domain < ApplicationRecord
 
   validate :statuses_uniqueness
 
-  validate :validate_admin_contact_type
-
   def security_level_resolver
     resolver = Dnsruby::Resolver.new(nameserver: Dnskey::RESOLVERS)
     resolver.do_validation = true
@@ -862,20 +860,7 @@ class Domain < ApplicationRecord
     return true if registrant.org?
     return false unless registrant.priv?
     
-    case registrant.ident_type
-    when 'birthday'
-      birth_date = Date.parse(registrant.ident)
-      calculate_age(birth_date) < 18
-    when 'priv'
-      if registrant.ident_country_code == 'EE' && registrant.ident.match?(/^\d{11}$/)
-        birth_date = parse_estonian_id_birth_date(registrant.ident)
-        calculate_age(birth_date) < 18
-      else
-        false
-      end
-    else
-      false
-    end
+    underage_registrant?
   end
 
   def require_tech_contacts?
@@ -884,6 +869,33 @@ class Domain < ApplicationRecord
 
   private
 
+  def underage_registrant?
+    case registrant.ident_type
+    when 'birthday'
+      underage_by_birthday?
+    when 'priv'
+      underage_by_estonian_id?
+    else
+      false
+    end
+  end
+
+  def underage_by_birthday?
+    birth_date = Date.parse(registrant.ident)
+    calculate_age(birth_date) < 18
+  end
+
+  def underage_by_estonian_id?
+    return false unless estonian_id?
+    
+    birth_date = parse_estonian_id_birth_date(registrant.ident)
+    calculate_age(birth_date) < 18
+  end
+
+  def estonian_id?
+    registrant.ident_country_code == 'EE' && registrant.ident.match?(/^\d{11}$/)
+  end
+
   def calculate_age(birth_date)
     ((Time.zone.now - birth_date.to_time) / 1.year.seconds).floor
   end
@@ -904,12 +916,4 @@ class Domain < ApplicationRecord
                  
     Date.parse("#{birth_year}-#{month}-#{day}")
   end
-
-  def validate_admin_contact_type
-    admin_contacts.each do |contact|
-      if contact.org?
-        errors.add(:admin_contacts, 'Admin contact must be a private person')
-      end
-    end
-  end
 end