Index listener

[ghost]

Adds Hyrax.publisher.subscribe(Hyrax::Listeners::MetadataIndexListener.new) to config/initializers/listeners.rb

Adds publishing an object.metadata.updated event to the after_create_concern callback.

[ghost]

@no-reply I backed out the additional method, and passing the Indexer to the adapter. The problem with the latter that I was seeing in the console is the same issue with the ValykrieIndexer.for not retrieving the right Indexer that I'm hoping to fix in #4221.