KvOutbox

new KvOutbox(kv, table?): KvOutbox;

put(
   input, 
   now, 
   lease?
): Promise<{
  status: "created" | "exists";
  record: OutboxRecord;
}>;

begin(key, o): Promise<OutboxRecord | null>;

markSent(
   key, 
   token, 
   result, 
   now
): Promise<void>;

extend(
   key, 
   token, 
   leaseUntil
): Promise<void>;

markFailed(
   key, 
   token, 
   error, 
   o
): Promise<void>;

claimDue(o): Promise<ClaimedSend[]>;

resolveAmbiguous(
   key, 
   token, 
   to, 
   now
): Promise<void>;

get(key): Promise<OutboxRecord | undefined>;

list(filter?): Promise<OutboxRecord[]>;

retry(key, now): Promise<void>;

discard(key): Promise<void>;

purge(o): Promise<number>;