respect the lease crawler's "min lease time remaining" configuration on the calculate endpoint

The price calculator endpoint is meant to help clients estimate how long they can store some data. It does this by reporting the cost for one lease period for an amount of data to store alongside the length of a lease period.

Since the lease crawler can be configured to renew leases before they expire, the reported lease period is likely always an overestimate. Since the min lease time remaining is now present in the configuration (and since users can change it, now) it can and should be incorporated into the price calculator endpoint's result.