Is there a way to set up the permissions so that a player can right-click and interact with blocks but not break anything?

Yes, but why would you even want all blocks to be usable? Right-clicking some blocks pretty much breaks them and people will be able to place items the use of which is allowed.

on my server, i have a spawn area which i want to be protected from block breaking, and i set up a shop with vending machines using the lightman's currency mod so i want people to only be able to right-click on things in that chunk but not break anything

Configure an exception for vending machines, not all blocks.

how do i do that ?

I want to be able to have a shop where people can not destroy any blocks but they can Click on things and interact.

It's all explained in the main config file.