For a given portal, return a time-ordered list of subscription changes.
Notes on the API
- Timeline items will be returned in reverse-chronological order.
- Query parameters offset and limit are used to paginate results.
- The returned property offset is an opaque token used internally to keep track of the position in the result set. It is not meant to be used for anything other than subsequent requests on this endpoint. Further, it is not meant to be long-lived.