Add support for displaying unknown servers on /admin/instances/:domain (#27150)

app/controllers/admin/instances_controller.rb

@@ -49,7 +49,7 @@ module Admin
     private
 
     def set_instance
-      @instance = Instance.find(TagManager.instance.normalize_domain(params[:id]&.strip))
+      @instance = Instance.find_or_initialize_by(domain: TagManager.instance.normalize_domain(params[:id]&.strip))
     end
 
     def set_instances

app/views/admin/instances/show.html.haml

@@ -7,6 +7,7 @@
     = ' - '
     = l(@time_period.last)
 
+  - if @instance.persisted?
     %p
       = fa_icon 'info fw'
       = t('admin.instances.totals_time_period_hint_html')
@@ -28,6 +29,9 @@
         = react_admin_component :dimension, dimension: 'instance_accounts', start_at: @time_period.first, end_at: @time_period.last, params: { domain: @instance.domain }, limit: 8, label: t('admin.instances.dashboard.instance_accounts_dimension')
       .dashboard__item
         = react_admin_component :dimension, dimension: 'instance_languages', start_at: @time_period.first, end_at: @time_period.last, params: { domain: @instance.domain }, limit: 8, label: t('admin.instances.dashboard.instance_languages_dimension')
+  - else
+    %p
+      = t('admin.instances.unknown_instance')
 
 %hr.spacer/
 
@@ -62,6 +66,7 @@
   - else
     = link_to t('admin.domain_blocks.add_new'), new_admin_domain_block_path(_domain: @instance.domain), class: 'button'
 
+- if @instance.persisted?
   %hr.spacer/
 
   %h3= t('admin.instances.availability.title')

config/locales/en.yml

@@ -534,6 +534,7 @@ en:
       total_reported: Reports about them
       total_storage: Media attachments
       totals_time_period_hint_html: The totals displayed below include data for all time.
+      unknown_instance: There is currently no record of this domain on this server.
     invites:
       deactivate_all: Deactivate all
       filter: