Partials (#3070)

* Remove GroupDMChannels

they sparked no joy

* Start partials for message deletion

* MessageUpdate partials

* Add partials as an opt-in client option

* Add fetch() to Message

* Message.author should never be undefined

* Fix channels being the wrong type

* Allow fetching channels

* Refactor and add reaction add partials

* Reaction remove partials

* Check for emoji first

* fix message fetching

janky

* User partials in audit logs

* refactor overwrite code

* guild member partials

* partials as a whitelist

* document GuildMember#fetch

* fix: check whether a structure is a partial, not whether cache is true

* typings: Updated for latest commit (#3075)

* partials: fix messageUpdate behaviour (now "old" message can be partial)

* partials: add warnings and docs

* partials: add partials to index.yml

* partials: tighten "partial" definitions

* partials: fix embed-only messages counting as partials

src/client/Client.js

@@ -434,6 +434,9 @@ class Client extends BaseClient {
     if (typeof options.disableEveryone !== 'boolean') {
       throw new TypeError('CLIENT_INVALID_OPTION', 'disableEveryone', 'a boolean');
     }
+    if (!(options.partials instanceof Array)) {
+      throw new TypeError('CLIENT_INVALID_OPTION', 'partials', 'an Array');
+    }
     if (typeof options.restWsBridgeTimeout !== 'number' || isNaN(options.restWsBridgeTimeout)) {
       throw new TypeError('CLIENT_INVALID_OPTION', 'restWsBridgeTimeout', 'a number');
     }