feat: add support for guild templates

[izexi]

• Ref: Server Templates part 2 discord/discord-api-docs#2144
• Continuation of feat: create 'GuildTemplate' & add 'Client#fetchGuildTemplate()' #4906 (branched from there and separated this into another PR since the referenced PR of the docs above containing these changes hasn't been merged yet)

Here's a snippet of how I tested these changes

import { once } from 'events';
import { Client, GuildTemplate } from 'discord.js';
import { TEST_GUILD_ID, TOKEN } from './constants';

const client = new Client();
let createdChannel;

client.login(TOKEN);

test('Client#fetchGuildTemplate() & GuildTempalte#createGuild()', async () => {
  await once(client, 'ready');

  const guild = client.guilds.cache.get(TEST_GUILD_ID);

  const template = await guild.createTemplate('bar');
  expect(template).toBeInstanceOf(GuildTemplate);

  await guild
    .fetchTemplates()
    .then((templates) =>
      expect(templates.size === 1 && templates.has(template.code)).toBe(true)
    );

  await template
    .edit({ description: 'baz' })
    .then((t) => expect(t.description).toBe('baz'));

  const createdChannelName = 'qux';
  createdChannel = await guild.channels.create(createdChannelName);
  await template
    .sync()
    .then((t) =>
      expect(
        t.serializedGuild.channels.some(
          ({ name }) => name === createdChannelName
        )
      ).toBe(true)
    );

  await template.delete();
  await expect(
    client.fetchGuildTemplate(template.code).catch(() => null)
  ).resolves.toBe(null);
});

afterAll(() => createdChannel.delete());

Status

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

Semantic versioning classification:

• This PR changes the library's interface (methods or parameters added)
  • This PR includes breaking changes (methods removed or renamed, parameters moved or removed)
• This PR only includes non-code changes, like changes to documentation, README, etc.

[advaith1]

docs PR has been merged

[SpaceEEC]

You could also add the error 30031 (A server can only have a single template.).
See: discord/discord-api-docs#2143 (comment)

Stale