api: fix timezone issue in repo pagination

As lists of repositories are sorted and paginated by their "updated"
timestamp, a cursor carries such a timestamp, so that the next query can
pick up where the last one left off. However, the passing of this
timestamp is broken on systems that do not run on UTC.

Go translates time values to the system's timezone, but this timezone
information gets lost when handing the value to postgres, presumably
because the column type is "timestamp without time zone".

Avoid the issue by converting the parsed timestamp back to UTC right
away.

api/graph/model/repository.go

@@ -103,7 +103,7 @@ func (r *Repository) QueryWithCursor(ctx context.Context,
 
 	if cur.Next != "" {
 		ts, _ := strconv.ParseInt(cur.Next, 10, 64)
-		updated := time.UnixMicro(ts)
+		updated := time.UnixMicro(ts).UTC()
 		q = q.Where(database.WithAlias(r.alias, "updated")+"<= ?", updated)
 	}
 	q = q.