simplify round stats fetch now that we don't need the round with it

modules/relay/src/main/RelayStatsApi.scala

@@ -19,28 +19,15 @@ final class RelayStatsApi(roundRepo: RelayRoundRepo, colls: RelayColls)(using sc
  // on measurement by minute at most; the storage depends on it.
  scheduler.scheduleWithFixedDelay(2 minutes, 2 minutes)(() => record())
 
- def get(id: RelayRoundId): Fu[Option[RoundStats]] =
- colls.round
- .aggregateOne(): framework =>
- import framework.*
- Match($id(id)) -> List(
- Project($doc("_id" -> true)),
- PipelineOperator(
- $lookup.simple(colls.stats, "stats", "_id", "_id")
- ),
- AddFields($doc("stats" -> $doc("$first" -> "$stats")))
- )
- .map: docOpt =>
- for
- doc <- docOpt
- stats <- doc.getAsOpt[Bdoc]("stats")
- data <- stats.getAsOpt[List[Int]]("d")
- viewers = data
- .grouped(2)
- .collect:
- case List(minute, crowd) => (minute, crowd)
- .toList
- yield RoundStats(viewers)
+ def get(id: RelayRoundId): Fu[RoundStats] =
+ colls.stats
+ .primitiveOne[List[Int]]($id(id), "d")
+ .mapz:
+ _.grouped(2)
+ .collect:
+ case List(minute, crowd) => (minute, crowd)
+ .toList
+ .map(RoundStats.apply)
 
  def setActive(id: RelayRoundId) = activeRounds.put(id)