// TODO this is set to zero-length byte pending decision on protocol for initial message, whether it should include message or not, and how to trigger the initial message so that current state of MRU is sent upon subscription
// TODO this is set to zero-length byte pending decision on protocol for initial message, whether it should include message or not, and how to trigger the initial message so that current state of Swarm feed is sent upon subscription
// Uses the Mutable Resource metadata currently loaded in the resources map entry.
// It is the caller's responsibility to make sure that this data is not stale.
// Note that a Mutable Resource update cannot span chunks, and thus has a MAX NET LENGTH 4096, INCLUDING update header data and signature. An error will be returned if the total length of the chunk payload will exceed this limit.
// Update publishes a feed update
// Note that a feed update cannot span chunks, and thus has a MAX NET LENGTH 4096, INCLUDING update header data and signature.
// This results in a max payload of `maxUpdateDataLength` (check update.go for more details)
// An error will be returned if the total length of the chunk payload will exceed this limit.
// Update can only check if the caller is trying to overwrite the very last known version, otherwise it just puts the update