Access control mechanism for settle function

[fedgiac]

Define the role of "owner" of the contract, which is expected to appoint and dismiss solvers.
Define the role of "solver", who can call the settle function.

[bh2smith]

Could implement a contract exposing a function canSolve(address) -> bool that the settlement contract can call into to determine is the solver is allowed. Sort of like a curated list. This could eventually be replaced with a staking and slashing mechanism

[nlordell]

@josojo and I have a brief discussion on Slack, this is how we imagined it:

We have a contract called SolverAllowList. This contract can have any owner and maybe even a proxy infrastrucutre. The dao is the owner and manages all solvers within this SolverAllowList contract.
The settlement contract has a modifier onlySolver and this modifier calls into the SolverAllowList
to check whether a solver is allowlisted.
In this case, the settlement contract does not have an owner at all.