Certifications also have a writability expiry date
Original change in https://github.com/ucoin-io/ucoin/issues/128
Protocol rule: https://github.com/ucoin-io/ucoin/blob/master/doc/Protocol.md#certification-writability
A certification written now has a sigWindow * avgGenTime
delay to be written, otherwise it is considered too old and will be rejected.
This rule is mainly here to avoid spam.
Possible Sakia bevavior
Certifications sent by uCoin nodes with a too old age should either:
- no more be displayed by Sakia
- be displayed but with a color saying "certification failed to be written and will never succeed"