feat: db models

Models/Database/PlayerMission.cs

@@ -0,0 +1,12 @@
+namespace GamificationService.Models.Database;
+
+public class PlayerMission
+{
+    public long Id { get; set; }
+    public long PlayerId { get; set; }
+    public required Player Player { get; set; }
+    public long MissionId { get; set; }
+    public required Mission Mission { get; set; }
+    public DateTime? Completed { get; set; }
+    public DateTime? RewardsRedeemed { get; set; }
+}