function update (_id, value, db = 'data', upsert = true) {
  const updates = dbNames.includes(db)
    ? {
        $set: {
          ...encObj(value)
        }
      }
    : {
        $set: {
          value
        }
      }
  return dbAction(db, 'update', {
    _id
  }, safeParse(updates), {
    upsert
  })
}
upsert single data in db
@param {string} _id
@param {any} value
@param {string} db default is 'data'