If you have the moxy, ignore the text and turn up to work on monday going on about how your phone was stolen on holiday. Make him earn his manager title
Absolutely this.
Bowl up bright and bushy tailed, ready to get going and be very, very positive about how good it is to be back at work. Get there earlier than your boss if you can as well so you’re already working when he arrives.
Text is a horribly cowardly way of releasing someone, make him earn his keep by telling you in person. And make sure you negotiate a much, much better exit package than 1 weeks notice, this’ll be much easier in person for you and much harder to turn down for him.
However, you do need to keep calm, serene almost, whilst you do this, don’t show your anger just yet.
Oh, and yes, the 1 weeks notice is legal for under 2 years service.