payloadLifespan/payloadLifetime and other name variants unified to Time To Live naming.

code/MessengerApi.Db/Repositories/MessageRepository.cs

@@ -16,7 +16,7 @@ namespace MessengerApi.Db.Repositories
 
             return this.db
                 .Where(x => x.ToId == user.Id && x.IsDelivered == false)
-                .Where(x => x.PayloadLifespanInSeconds == null || x.CreatedUtc.AddSeconds(x.PayloadLifespanInSeconds.Value) >= timestamp)
+                .Where(x => x.TimeToLiveInSeconds == null || x.CreatedUtc.AddSeconds(x.TimeToLiveInSeconds.Value) >= timestamp)
                 .OrderBy(x => x.CreatedUtc);
         }
     }