Retrieve the organisation tree expanded from top accessible node to the specified node.
Returns the full path from the top accessible node to the requested node, with all ancestor branches expanded.

• data: Top level nodes (children of the top accessible organisation node)
• included: All expanded nodes at deeper levels
• meta: Contains the requested_node_id and top_accessible_organisation_node_id

Each node includes references to its children via relationships.children.data.

🔒 External clients call this endpoint with an OAC (Organisation Access Credentials — ⚠️ Beta) access token carrying the organisations:read scope.

Access validation: The OAC token's organisation_node must be an ancestor of (or equal to) the requested node. The top_accessible_organisation_node_id in the response indicates the highest node accessible with the current token.