user can pass a solverFee lower than the verificationFee

[CluEleSsUK]

and in fact here, we should probably check that solverFee - verification > 0, because in principle the fee could be too low:

onlyswaps-solidity/src/Router.sol

Line 147 in f0266fd

require(solverFee > 0, ErrorsLib.FeeTooLow());

Originally posted by @CluEleSsUK in randa-mu/dcipher#145 (comment)