Make admin contacts optional for private registrants

This change makes admin contacts optional for private registrants while keeping them mandatory for organizations. The changes include:

- Updated Domain model validations to make admin and tech contacts optional (min=0) for private registrants
- Added validation rules methods to handle different requirements based on registrant type
- Modified EPP domain creation to support domains without admin contacts for private registrants
- Updated attach_default_contacts to skip adding contacts for private registrants
- Added comprehensive test coverage for:
  - Domain model validations with private/org registrants
  - EPP domain creation without admin contacts for private registrants
  - REPP API contact management for private registrants

This implements the requirement to make admin contacts optional for private registrations of .ee domains while maintaining the existing validation rules for organizations.

test/integration/epp/domain/create/base_test.rb

@@ -436,6 +436,9 @@ class EppDomainCreateBaseTest < EppTestCase
     contact = contacts(:john)
     registrant = contact.becomes(Registrant)
 
+    registrant.update!(ident_type: 'org')
+    registrant.reload
+
     request_xml = <<-XML
       <?xml version="1.0" encoding="UTF-8" standalone="no"?>
       <epp xmlns="#{Xsd::Schema.filename(for_prefix: 'epp-ee', for_version: '1.0')}">
@@ -444,6 +447,7 @@ class EppDomainCreateBaseTest < EppTestCase
             <domain:create xmlns:domain="#{Xsd::Schema.filename(for_prefix: 'domain-ee', for_version: '1.2')}">
               <domain:name>#{name}</domain:name>
               <domain:registrant>#{registrant.code}</domain:registrant>
+              <domain:contact type="admin">#{contact.code}</domain:contact>
             </domain:create>
           </create>
           <extension>
@@ -937,4 +941,54 @@ class EppDomainCreateBaseTest < EppTestCase
     ENV["shunter_default_threshold"] = '10000'
     ENV["shunter_enabled"] = 'false'
   end
+
+  def test_registers_new_domain_with_private_registrant_without_admin_contacts
+    now = Time.zone.parse('2010-07-05')
+    travel_to now
+    name = "new.#{dns_zones(:one).origin}"
+    contact = contacts(:john)
+    registrant = contact.becomes(Registrant)
+
+    registrant.update!(ident_type: 'priv')
+    registrant.reload
+    assert_not registrant.org?
+
+    request_xml = <<-XML
+      <?xml version="1.0" encoding="UTF-8" standalone="no"?>
+      <epp xmlns="#{Xsd::Schema.filename(for_prefix: 'epp-ee', for_version: '1.0')}">
+        <command>
+          <create>
+            <domain:create xmlns:domain="#{Xsd::Schema.filename(for_prefix: 'domain-ee', for_version: '1.2')}">
+              <domain:name>#{name}</domain:name>
+              <domain:registrant>#{registrant.code}</domain:registrant>
+            </domain:create>
+          </create>
+          <extension>
+            <eis:extdata xmlns:eis="#{Xsd::Schema.filename(for_prefix: 'eis', for_version: '1.0')}">
+              <eis:legalDocument type="pdf">#{'test' * 2000}</eis:legalDocument>
+            </eis:extdata>
+          </extension>
+        </command>
+      </epp>
+    XML
+
+    assert_difference 'Domain.count' do
+      post epp_create_path, params: { frame: request_xml },
+           headers: { 'HTTP_COOKIE' => 'session=api_bestnames' }
+    end
+    response_xml = Nokogiri::XML(response.body)
+    assert_correct_against_schema response_xml
+
+    assert_epp_response :completed_successfully
+
+    domain = Domain.find_by(name: name)
+    assert_equal name, domain.name
+    assert_equal registrant, domain.registrant
+    assert_empty domain.admin_contacts
+    assert_empty domain.tech_contacts
+    assert_not_empty domain.transfer_code
+
+    default_registration_period = 1.year + 1.day
+    assert_equal now + default_registration_period, domain.expire_time
+  end
 end