Add bulk replace to registrar area

#662

app/models/tech_domain_contact.rb

@@ -1,2 +1,23 @@
 class TechDomainContact < DomainContact
+  # Audit log is needed, therefore no raw SQL
+  def self.replace(predecessor, successor)
+    affected_domains = []
+    skipped_domains = []
+    tech_contacts = where(contact: predecessor)
+
+    transaction do
+      tech_contacts.each do |tech_contact|
+        if tech_contact.domain.discarded?
+          skipped_domains << tech_contact.domain.name
+          next
+        end
+
+        tech_contact.contact = successor
+        tech_contact.save!
+        affected_domains << tech_contact.domain.name
+      end
+    end
+
+    return affected_domains.sort, skipped_domains.sort
+  end
 end