Fixed heatmap not working in mssql (#5248)

models/user_heatmap.go

 func GetUserHeatmapDataByUser(user *User) ([]*UserHeatmapData, error) {
 	hdata := make([]*UserHeatmapData, 0)
 	var groupBy string
+	var groupByName = "timestamp" // We need this extra case because mssql doesn't allow grouping by alias
 	switch {
 	case setting.UseSQLite3:
 		groupBy = "strftime('%s', strftime('%Y-%m-%d', created_unix, 'unixepoch'))"
 		groupBy = "extract(epoch from date_trunc('day', to_timestamp(created_unix)))"
 	case setting.UseMSSQL:
 		groupBy = "dateadd(DAY,0, datediff(day,0, dateadd(s, created_unix, '19700101')))"
+		groupByName = groupBy
 	}
 
-	err := x.Select(groupBy+" as timestamp, count(user_id) as contributions").
+	err := x.Select(groupBy+" AS timestamp, count(user_id) as contributions").
 		Table("action").
 		Where("user_id = ?", user.ID).
 		And("created_unix > ?", (util.TimeStampNow() - 31536000)).
-		GroupBy("timestamp").
+		GroupBy(groupByName).
 		OrderBy("timestamp").
 		Find(&hdata)
 	return hdata, err