feeAbsolute
Set an absolute fee The fee_absolute method refers to the absolute transaction fee in Amount. If anyone sets both the fee_absolute method and the fee_rate method, the FeePolicy enum will be set by whichever method was called last, as the FeeRate and FeeAmount are mutually exclusive.
Note that this is really a minimum absolute fee – it’s possible to overshoot it slightly since adding a change output to drain the remaining excess might not be viable.