feat: add ranked season window policy

server/domain/season_test.go

@@ -1,6 +1,9 @@
 package domain
 
-import "testing"
+import (
+	"testing"
+	"time"
+)
 
 func TestRankedProvisionalBoundaryIsFirstTenGames(t *testing.T) {
 	for games := 0; games < 10; games++ {
@@ -57,3 +60,18 @@ func TestCasualRatingHasNoSeasonOperation(t *testing.T) {
 		t.Fatal("casual boundary test fixture unexpectedly provisional")
 	}
 }
+
+func TestRankedSeasonWindowIsExactlyTwelveWeeksAndDueIsIdempotent(t *testing.T) {
+	start := time.Unix(1000, 0)
+	season, err := NewRankedSeason("season-1", start)
+	if err != nil || season.EndsAt.Sub(start) != RankedSeasonLength {
+		t.Fatalf("season = %+v err=%v", season, err)
+	}
+	if SeasonRolloverDue(season, season.EndsAt.Add(-time.Nanosecond)) || !SeasonRolloverDue(season, season.EndsAt) {
+		t.Fatal("season due boundary is wrong")
+	}
+	season.RolledOverAt = season.EndsAt
+	if SeasonRolloverDue(season, season.EndsAt.Add(time.Hour)) {
+		t.Fatal("completed season remained due")
+	}
+}