Record the original object creation time

From @alikic on Sun Jun 05 2016 00:52:21 GMT+0000 (UTC)

If I read the code correctly, dht only remembers the time when the local node received the object. For use cases typical for enterprises (which may imply a private network), like data archiving and expiry, it is required that there is a concept of object creation time at the network level. While some use cases can get away with pinning to a local node (who is interested in keeping the object around), some other use cases which involve moving data between nodes (e.g. archiving and later recovering from the archive) cannot.

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