[SAGA-RG] Final Call: advert extension

Hi all, attached is the latest draft of the SAGA Advert API extension, which includes changes as agreed on the last call. If there are no comments to the contrary, I'd like to submit that draft to the editor at the end of the week. Please have a close look at the object serialization description - that is the part that changed most over the last month or so. Also, the TTL management has changed somewhat compared to the draft discussed at last OGF. Best, Andre. -- Nothing is ever easy.