Add setting to disable the anti-spam (#11296)

* Add environment variable to disable the anti-spam

* Move antispam setting to admin settings

* Fix typo

* antispam → spam_check

app/models/form/admin_settings.rb

@@ -28,6 +28,7 @@ class Form::AdminSettings
     thumbnail
     hero
     mascot
+    spam_check_enabled
   ).freeze
 
   BOOLEAN_KEYS = %i(
@@ -39,6 +40,7 @@ class Form::AdminSettings
     show_known_fediverse_at_about_page
     preview_sensitive_media
     profile_directory
+    spam_check_enabled
   ).freeze
 
   UPLOAD_KEYS = %i(