Add serializing/unserializing of "locked" actor attribute (#4585)

app/lib/activitypub/adapter.rb

@@ -5,6 +5,10 @@ class ActivityPub::Adapter < ActiveModelSerializers::Adapter::Base
     :camel_lower
   end
 
+  def self.transform_key_casing!(value, _options)
+    ActivityPub::CaseTransform.camel_lower(value)
+  end
+
   def serializable_hash(options = nil)
     options = serialization_options(options)
     serialized_hash = { '@context': ActivityPub::TagManager::CONTEXT }.merge(ActiveModelSerializers::Adapter::Attributes.new(serializer, instance_options).serializable_hash(options))