How would a city siege go in Pathfinder 2E?

I am preparing a sandbox quest for my level 7 players, where they go to a city that is currently assieged by bandits and mercenaries lead by an Oni and they need to help the inhabitants by ending the siege somehow. The whole thing is supposed to take like 3 sessions.

I was preparing the usual stuff when a question hit me : how would a siege go in this system, exactly?

I mean, in our times, without magic, I can get the basic principles of a city siege (starve the city inhabitants, cut or poison the water supplies...), but with spells like Create food, water (or just cure it), and spells like Invisibility, Command... stuff like that, how exactly would a siege go in this setting ? I mean not necessarily in a realistic way, but in a fun, engaging way for the players, that would be distinct from the usual siege stuff ?

Do you have any fun ideas ?