Instances list in admin (#2095)

* Add admin/instances index action

* Add link to instances admin page

* View lists instances

* Instances, grouped by domain, ordered by count

* Use Account.remote scope

* Extract method: Account.by_domain_accounts

config/locales/en.yml

@@ -114,6 +114,10 @@ en:
         undo: Undo
       title: Domain Blocks
       undo: Undo
+    instances:
+      account_count: Accounts
+      domain_name: Domain name
+      title: Instances
     pubsubhubbub:
       callback_url: Callback URL
       confirmed: Confirmed

config/navigation.rb

@@ -17,6 +17,7 @@ SimpleNavigation::Configuration.run do |navigation|
     primary.item :admin, safe_join([fa_icon('cogs fw'), t('admin.title')]), admin_reports_url, if: proc { current_user.admin? } do |admin|
       admin.item :reports, safe_join([fa_icon('flag fw'), t('admin.reports.title')]), admin_reports_url, highlights_on: %r{/admin/reports}
       admin.item :accounts, safe_join([fa_icon('users fw'), t('admin.accounts.title')]), admin_accounts_url, highlights_on: %r{/admin/accounts}
+      admin.item :instances, safe_join([fa_icon('cloud fw'), t('admin.instances.title')]), admin_instances_url, highlights_on: %r{/admin/instances}
       admin.item :pubsubhubbubs, safe_join([fa_icon('paper-plane-o fw'), t('admin.pubsubhubbub.title')]), admin_pubsubhubbub_index_url
       admin.item :domain_blocks, safe_join([fa_icon('lock fw'), t('admin.domain_blocks.title')]), admin_domain_blocks_url, highlights_on: %r{/admin/domain_blocks}
       admin.item :sidekiq, safe_join([fa_icon('diamond fw'), 'Sidekiq']), sidekiq_url, link_html: { target: 'sidekiq' }

config/routes.rb

@@ -80,6 +80,7 @@ Rails.application.routes.draw do
     resources :pubsubhubbub, only: [:index]
     resources :domain_blocks, only: [:index, :new, :create, :show, :destroy]
     resources :settings, only: [:index, :update]
+    resources :instances, only: [:index]
 
     resources :reports, only: [:index, :show, :update] do
       resources :reported_statuses, only: :destroy