* ensure sync duties for next epoch are registered in time
For attestations, VC queries duties for current and next epoch.
For sync messages, VC queries for current and next period (if soon).
This means that for sync messages we don't actually have the duties for
next epoch in all situations, leading to situation where VC may miss
sync duties in the final slot of an epoch when using. As duties remain
same within a sync committee period, simply copy them over to next epoch
to avoid this situation without adding network latency.
* Update beacon_chain/validator_client/duties_service.nim
Co-authored-by: Jacek Sieka <jacek@status.im>
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Co-authored-by: Jacek Sieka <jacek@status.im>