Make LDN messages COAR compliant

[qqmyers]

Overview of the Feature Request As part of the post-MVP continuation of Harvard Data Commons (HDC), there is support for updating the LDN messaging capabilities added in #8775 to use the syntax being defined by COAR for announcing relationships. This is primarily an update of the syntax in the JSON-LD LDN messages being sent. However, as a consequence of COAR's decision to not allow additional metadata to be sent in the message, new logic to retrieve the title of a remote resource is now needed to retain the ability to show that title in the notifications shown in Dataverse.

What inspired the request? HDC has been working with COAR to define a standard in this area and, now that a stable proposal for the standard exists, wants to update the new notification capability to use it.

Code in development.