`DateTime.fromString()` allows invalid ISO 8601 dates

[cedx]

An ISO date like 2000-13-48T00:00:00Z or 2000-01-01T29:73:82Z is invalid: the DateTime.fromString() method should throw an exception in this case.
Instead, it returns a date where the timestamp is adjusted according to the "overflow": 2001-01-17 00:00:00 for 2000-13-48T00:00:00Z, 2000-01-02 06:14:22 for 2000-01-01T29:73:82Z.