has_quest_rewards interface

The rewards GrantRewards pays to eligible memberships. Write it with SetRewards.

Grants every reward in Rewards, in array order, to the memberships whose Info has Receive and that CanReceive accepts for it, and returns the recipients of each reward whose Grant succeeded. An error means not everything was granted: rewards whose Grant succeeded stay granted, and the errors are every failing Grant's, concatenated.

Returns what GrantRewards would grant right now. A reward whose CanGrant refuses is omitted, and an empty list is a reward that pays nobody.

Replaces the reward list; nothing is granted and no event fires.

Succeeds if Membership may receive Reward from this quest; the default accepts everyone. A refusal drops that membership from that reward's list and is not an error.