Retrieves the activity records with the given IDs, limited to those logged against the given parent entity. IDs that do not exist, belong to another entity or are not visible to the caller are silently left out.

Authorization. The caller must be able to access the parent entity. No OAuth2 scope beyond a valid token is required.

Errors. 400 if no parent entity ID or no activity ID is given, and 400 with error code 40000 if the caller cannot access the parent entity; 404 if the parent entity does not exist in the caller's tenant.