Environment

Knex version: 0.21.15
Database + version: postgresql 13
OS: ubuntu

@lorefnon.

Bug

1. Explain what kind of behaviour you are getting and how you think it should do
   onConflict and merge should interact nicely with Knex.CompositeTableType

2. Error message
   for .onConflict: Argument of type 'string' is not assignable to parameter of type 'readonly ("base" | "insert" | "update")[]

for .merge: Argument of type '{ insert_only_field: string; }' is not assignable to parameter of type 'Readonly<Partial<MaybeRawRecord<CompositeTableType<DBUser, Pick<DBUser, "name" | "insert_only_field">, Pick<DBUser, "name">>>>>'. Object literal may only specify known properties, and 'insert_only_field' does not exist in type 'Readonly<Partial<MaybeRawRecord<CompositeTableType<DBUser, Pick<DBUser, "name" | "insert_only_field">, Pick<DBUser, "name">>>>>'

3. Reduced test code, for example in https://npm.runkit.com/knex or if it needs real
   database connection to MySQL or PostgreSQL, then single file example which initializes
   needed data and demonstrates the problem.

import Knex from "knex";
import knex from './client';

declare module "knex/types/tables" {
  interface DBUser {
    id: string;
    insert_only_field: string;
    name: string;
  }
  interface Tables {
    users: Knex.CompositeTableType<DBUser, 
       // insert
       Pick<DBUser, 'name' | 'insert_only_field'>,
       // update
      Pick<DBUser, 'name'>
    >;
  }
}

await knex('users')
    .insert({ name: "Bob", insert_only_field: "1" })
    .onConflict("insert_only_field") // type error here
    .merge({
      name: "Bob",
      insert_only_field: knex.raw("EXCLUDED.insert_only_field"), // raw also fails with different error
    })
      ;