refactor: rewrite message creation (#2774)

* Rework createMessage
- MessageAttachment is now structurally similar to FileOptions
- No longer mutates the object passed as options
- Supports more permutations of arguments

* Ignore complexity warning

* Refactor name finding

* Fix typo

* Update typings

* Default name to null for MessageAttachment

* Make Message#reply use transformOptions

* Move transformOptions

* Fix Message#reply

* Fix mutation

* Update tests

* Fix options passing

* Refactor into APIMessage

* Fix webhook send

* Expose APIMessage

* Add documentation

* Add types

* Fix type doc

* Fix another type doc

* Fix another another type doc (is this one even right!?)

* Remove trailing comma

* Properly clone split options

* Add support for sending file as stream

* Missed a doc

* Resolve files only once when splitting messages

* This looks nicer

* Assign directly

* Don't cache data and files

* Missing return type

* Use object spread instead Object.assign

* Document constructors

* Crawl is a little dot

* comp pls

* tests: sanitize local file path, disable no-await-in-loop

src/index.js

@@ -51,6 +51,7 @@ module.exports = {
   // Structures
   Base: require('./structures/Base'),
   Activity: require('./structures/Presence').Activity,
+  APIMessage: require('./structures/APIMessage'),
   CategoryChannel: require('./structures/CategoryChannel'),
   Channel: require('./structures/Channel'),
   ClientApplication: require('./structures/ClientApplication'),