username of the account performing the powerdown
amount of VESTS to powerdown
This table store the VESTS withdrawals (i.e. Powerdown) requests from users.
A powerdown request will be split into multiple virtual operations (see VOFillVestingWithdraws) at the pace of one per week (currently 13 weeks)
withdraw_vestingoperation issued from a user will reset the powerdown duration to 13 weeks if the previous one is not complete.