Error: Schema validation error: operation hooks were not added to the following fields: Mutation.createUser
Posted this before, but at the wrong place i guess :) 

I would like to wrap an existing mutation so that i can do something after the insert.
I followed the guide at: [makeWrapResolversPlugin (graphile-utils)](https://www.graphile.org/postgraphile/make-wrap-resolvers-plugin/#method-1-wrapping-individual-resolvers-of-known-fields)

I have a mutation called createUser and i can see and use it in graphiql.

On startup, i get the following error.

> Error: Schema validation error: operation hooks were not added to the following fields: Mutation.createUser

```
makeWrapResolversPlugin({
  Mutation: {
    async createUser(resolve, source, args, context, resolveInfo) {
      await resolve(source, args, context, resolveInfo);
      // do something
    },
  },
}),
```
Why is that?

Thanks!