Add registrar nameserver replacement UI

#661

config/locales/registrar/domains.en.yml

@@ -5,6 +5,7 @@ en:
         header: Domains
         new_btn: New domain
         transfer_btn: Transfer
+        replace_nameserver_btn: Replace nameserver
         csv:
           domain_name: Domain
           transfer_code: Transfer code

config/locales/registrar/registrar_nameservers.en.yml

@@ -0,0 +1,12 @@
+en:
+  registrar:
+    registrar_nameservers:
+      edit:
+        header: Replace nameserver
+        replace_btn: Replace
+
+      form:
+        replace_btn: Replace nameserver
+
+      update:
+        replaced: Nameserver have been successfully replaced

config/routes.rb

@@ -62,6 +62,8 @@ Rails.application.routes.draw do
       end
     end
     resources :domain_transfers, only: %i[new create]
+    get 'registrar/nameservers', to: 'registrar_nameservers#edit', as: :edit_registrar_nameserver
+    put 'registrar/nameservers', to: 'registrar_nameservers#update', as: :update_registrar_nameserver
 
     resources :contacts, constraints: {:id => /[^\/]+(?=#{ ActionController::Renderers::RENDERERS.map{|e| "\\.#{e}\\z"}.join("|") })|[^\/]+/} do
       member do