OptionalassetThe link to create. asset_type, asset_scope_id, and asset_id are
required. The server assigns name and create_time; the path supplies
the page and category. A duplicate target in that category returns the
existing link.
OptionalparentCategory collection on the page in which to create the link.
Format: pages/{page_id}/asset-link-categories/{category}, where
{category} is a LinkCategory value (SOURCE or RELATED_ASSETS).
Request for CreateAssetLink.