feat: add age validation for admin contacts

- Add AgeValidation module for consistent age checks
- Validate admin contacts must be at least 18 years old
- Move age validation logic from Domain to shared module
- Add tests for admin contact age validation
- Fix JSON format for admin_contacts_allowed_ident_type setting

This change ensures that administrative contacts must be adults (18+),
using the same age validation logic as for registrants. The validation
works with both birthday and Estonian ID formats. Settings are now
properly stored as JSON strings for consistent parsing.

app/models/admin_domain_contact.rb

@@ -1,4 +1,8 @@
 class AdminDomainContact < DomainContact
+  include AgeValidation
+  
+  validate :validate_contact_age
+
   # rubocop:disable Metrics/AbcSize
   # rubocop:disable Metrics/MethodLength
   def self.replace(current_contact, new_contact)
@@ -23,4 +27,14 @@ class AdminDomainContact < DomainContact
   end
   # rubocop:enable Metrics/AbcSize
   # rubocop:enable Metrics/MethodLength
+
+  private
+
+  def validate_contact_age
+    return unless contact&.underage?
+
+    errors.add(:contact, I18n.t(
+      'activerecord.errors.models.admin_domain_contact.contact_too_young'
+    ))
+  end
 end

app/models/concerns/age_validation.rb

@@ -0,0 +1,53 @@
+module AgeValidation
+  extend ActiveSupport::Concern
+
+  def underage?
+    case ident_type
+    when 'birthday'
+      underage_by_birthday?
+    when 'priv'
+      underage_by_estonian_id?
+    else
+      false
+    end
+  end
+
+  private
+
+  def underage_by_birthday?
+    birth_date = Date.parse(ident)
+    calculate_age(birth_date) < 18
+  end
+
+  def underage_by_estonian_id?
+    return false unless estonian_id?
+    
+    birth_date = parse_estonian_id_birth_date(ident)
+    calculate_age(birth_date) < 18
+  end
+
+  def estonian_id?
+    ident_country_code == 'EE' && ident.match?(/^\d{11}$/)
+  end
+
+  def calculate_age(birth_date)
+    ((Time.zone.now - birth_date.to_time) / 1.year.seconds).floor
+  end
+
+  def parse_estonian_id_birth_date(id_code)
+    century_number = id_code[0].to_i
+    year_digits = id_code[1..2]
+    month = id_code[3..4]
+    day = id_code[5..6]
+    
+    birth_year = case century_number
+                 when 1, 2 then "18#{year_digits}"
+                 when 3, 4 then "19#{year_digits}"
+                 when 5, 6 then "20#{year_digits}"
+                 else
+                   raise ArgumentError, "Invalid century number in Estonian ID"
+                 end
+                 
+    Date.parse("#{birth_year}-#{month}-#{day}")
+  end
+end 

app/models/contact.rb

@@ -10,6 +10,7 @@ class Contact < ApplicationRecord
   include Contact::Archivable
   include Contact::CompanyRegister
   include EmailVerifable
+  include AgeValidation
 
   belongs_to :original, class_name: 'Contact'
   belongs_to :registrar, required: true

app/models/domain.rb

@@ -12,6 +12,7 @@ class Domain < ApplicationRecord
   include Domain::Releasable
   include Domain::Disputable
   include Domain::BulkUpdatable
+  include AgeValidation
 
   PERIODS = [
     ['3 months', '3m'],
@@ -866,7 +867,7 @@ class Domain < ApplicationRecord
     return true if registrant.org? && Setting.admin_contacts_required_for_org
     return false unless registrant.priv?
     
-    underage_registrant? && Setting.admin_contacts_required_for_minors
+    registrant.underage? && Setting.admin_contacts_required_for_minors
   end
 
   def require_tech_contacts?
@@ -876,51 +877,7 @@ 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
-
-  def parse_estonian_id_birth_date(id_code)
-    century_number = id_code[0].to_i
-    year_digits = id_code[1..2]
-    month = id_code[3..4]
-    day = id_code[5..6]
-    
-    birth_year = case century_number
-                 when 1, 2 then "18#{year_digits}"
-                 when 3, 4 then "19#{year_digits}"
-                 when 5, 6 then "20#{year_digits}"
-                 else
-                   raise ArgumentError, "Invalid century number in Estonian ID"
-                 end
-                 
-    Date.parse("#{birth_year}-#{month}-#{day}")
+    registrant.underage?
   end
 
   def validate_admin_contacts_ident_type