solve
Solve this capd message (in preparation for sending) with the provided valid create time. if time is within a year of the epoch (or negative) consider it to be relative
Parameters
If null, do no change the createTime. Otherwise if time is within a year of the epoch (or negative) consider it to be relative to now seconds ago. Pass a positive number to backdate your message by that many seconds. Otherwise assume time is an absolute number. The default is to backdate by 5 seconds. Note that if your CAPD message appears to be created in the future it will be rejected.
A message's priority falls by 1 every CAPD_MSG_LIFETIME_SEC of age, counted from createTime. If the POW target was set with setPowTargetHarderThanPriority, the target is raised by (age / CAPD_MSG_LIFETIME_SEC) so the message still has the requested priority right now, despite being backdated. This is what the full node does in "capd send".