How to set default boolean field value on existing documents via migration script?

import {defineMigration, at, setIfMissing} from 'sanity/migrate'

export default defineMigration({
  title: 'Set isHighlighted to false for all posts',
  documentTypes: ['post'],
  
  migrate: {
    document(doc, context) {
      return at('isHighlighted', setIfMissing(false))
    }
  }
})

// scripts/setIsHighlighted.js
import {getCliClient} from 'sanity/cli'

const client = getCliClient()

const fetchDocuments = () => 
  client.fetch(`*[_type == "post" && !defined(isHighlighted)]`)

const buildPatches = docs =>
  docs.map(doc => ({
    id: doc._id,
    patch: {
      setIfMissing: {isHighlighted: false}
    }
  }))

const createTransaction = patches =>
  patches.reduce((tx, patch) => tx.patch(patch.id, patch.patch), client.transaction())

const commitTransaction = tx => tx.commit()

const migrateNextBatch = async () => {
  const documents = await fetchDocuments()
  if (documents.length === 0) {
    console.log('No more documents to migrate!')
    return
  }
  console.log(`Migrating batch of ${documents.length} documents...`)
  const patches = buildPatches(documents)
  const transaction = createTransaction(patches)
  await commitTransaction(transaction)
  await migrateNextBatch()
}

migrateNextBatch().catch(err => {
  console.error(err)
  process.exit(1)
})