[Docs]: Clarify that user attributes need to match their database column names

[dallenbaldwin]

Description

I was following the docs to put together a SvelteKit project using DrizzleORM and all was going super well until I started adding additional attributes to my users.

While I can see the quick solution is to just make the column names match the property names, I've seen instances where people expect those to be independent, especially when the ORM allows you to customize them independently.

It would probably be a good idea to update the docs to mention this behavior in the Users documentation

my user

export const users = sqliteTable('users', {
  /**
   * generated by lucia
   *
   * @see https://lucia-auth.com/basics/users/
   */
  id: text('id').primaryKey(),
  username: text('username').notNull(),
  /**
   * @default 'user'
   * @see {@link roles}
   */
  role: text('role', { enum: roles }).notNull(),
  /**
   * @default 'light'
   * @see {@link lightThemes}
   */
  lightTheme: text('light_theme', { enum: lightThemes }).notNull(),
  /**
   * @default 'dark'
   * @see {@link darkThemes}
   */
  darkTheme: text('dark_theme', { enum: darkThemes }).notNull(),
})

does not work

type User = import('$lib/server').User
...
  namespace Lucia {
    type Auth = import('$lib/server').Auth
    type DatabaseUserAttributes = Omit<User, 'id'>
    type DatabaseSessionAttributes = NonNullable<unknown>
  }

// create user with username method
const user = await auth.createUser({
  key: {
    providerId: 'username',
    password,
    // lowercase to ensure uniqueness
    providerUserId: username.toLowerCase(),
  },
  attributes: {
    username,
    role: 'user',
    darkTheme: 'dark',
    lightTheme: 'light',
  },
})

works

type User = import('$lib/server').User
...
  namespace Lucia {
    type Auth = import('$lib/server').Auth
    /**
     * these have to match the _database_ column names, not what you called them
     * in Drizzle's config
     */
    type DatabaseUserAttributes = {
      username: User['username']
      light_theme: User['lightTheme']
      dark_theme: User['darkTheme']
      role: User['role']
    }
    type DatabaseSessionAttributes = NonNullable<unknown>
  }

// create user with username method
const user = await auth.createUser({
  key: {
    providerId: 'username',
    password,
    // lowercase to ensure uniqueness
    providerUserId: username.toLowerCase(),
  },
  attributes: {
    username,
    role: 'user',
    dark_theme: 'dark',
    light_theme: 'light',
  },
})