If i overwrite extrahead in change_form.html class Media: js=[] does not work.

[italomaia]

If i create a custom change_form.html for a model, and overwrite the extrahead tag, js from class Media, in ModelAdmin is ignored. I believe the proper
behavior would be that both, the js defined libraries and the what's inside extrahead should coexist.

Reason? Because i do not want to add a library to my page to trigger a event in the page. So, i could add the mootools library to the ModelAdmin templates and trigger a slug_update method inside the extrahead.