How to make a filter required using nexus-prisma-plugin?

[HendrikJan]

I would like to filter my query results.
My code looks like this:

import { objectType, queryType } from '@nexus/schema'

export const Program = objectType({
  name: 'Program',
  definition(t) {
    t.model.id()
    t.model.name()
    // a Program also has a year_id on which I want to filter
  },
})

export const Query = queryType({
  definition(t) {
    t.crud.programs()
  },
})

This query works:

{
  programs {
    name
  }
}

But I would like to run a query like this, and I would like the year_id to be required:

{
  programs(year_id: 2) {
    name
  }
}

Is there an easy way a achieve this?
I tried t.crud.programs({ filtering: true }), but this seems not to do anything.

UPDATE:
I found out that using t.crud.programs({ filtering: true }) enables filtering like this:

{
  programs(where:{year_id:{equals:2}}) {
    name
  }
}

One thing left to find out: how can I make "year_id" required.

(I'll update the discussion title to reflect what I want to find out now)