The short answer — no, the Custom Channels API does not currently support HS_OBJECT_ID as a deliveryIdentifierType. The only supported values (as defined in the documentation) are:
• HS_EMAIL_ADDRESS
• HS_PHONE_NUMBER
• CHANNEL_SPECIFIC_OPAQUE_ID
in this case, hs_boject_id is not a routable address like an email or phone number. Custom Channels expect something that points to an actual messaging endpoint.
You’ll need to use another solution if you must use a contact’s id. For example, maintain a lookup table that associates a contact’s hs_object_id with your channels user identifier (stored under CHANNEL_SPECIFIC_OPAQUE_ID). Your code or middleware would do the matching when you need to send messages or log events.
Unfortunately, the documentation doesn’t like the underlying why for situations that fall under “not possible”.