Add support for indexable attribute on remote actors (#26485)

Co-authored-by: Eugen Rochko <eugen@zeonfederated.com>

app/services/activitypub/process_account_service.rb

@@ -115,6 +115,7 @@ class ActivityPub::ProcessAccountService < BaseService
     @account.fields                  = property_values || {}
     @account.also_known_as           = as_array(@json['alsoKnownAs'] || []).map { |item| value_or_id(item) }
     @account.discoverable            = @json['discoverable'] || false
+    @account.indexable               = @json['indexable'] || false
   end
 
   def set_fetchable_key!