refactor(Attachment): Merge MessageAttachment with Attachment (#1894)

* refactor(Attachment): Merge MessageAttachment with Attachment

* refactor(Attachment): Rename setup to _patch for consistency

* refactor(MessageAttachment): Global rename of Attachment class

src/structures/MessageAttachment.js

@@ -1,43 +1,88 @@
 /**
  * Represents an attachment in a message.
+ * @param {BufferResolvable|Stream} file The file
+ * @param {string} [name] The name of the file, if any
  */
 class MessageAttachment {
-  constructor(message, data) {
-    /**
-     * The client that instantiated this MessageAttachment
-     * @name MessageAttachment#client
-     * @type {Client}
-     * @readonly
-     */
-    Object.defineProperty(this, 'client', { value: message.client });
-
-    /**
-     * The message this attachment is part of
-     * @type {Message}
-     */
-    this.message = message;
-
-    this.setup(data);
+  constructor(file, name, data) {
+    this.file = null;
+    if (data) this._patch(data);
+    if (name) this.setAttachment(file, name);
+    else this._attach(file);
   }
 
-  setup(data) {
+  /**
+    * The name of the file
+    * @type {?string}
+    * @readonly
+    */
+  get name() {
+    return this.file.name;
+  }
+
+  /**
+    * The file
+    * @type {?BufferResolvable|Stream}
+    * @readonly
+    */
+  get attachment() {
+    return this.file.attachment;
+  }
+
+  /**
+    * Set the file of this attachment.
+    * @param {BufferResolvable|Stream} file The file
+    * @param {string} name The name of the file
+    * @returns {MessageAttachment} This attachment
+    */
+  setAttachment(file, name) {
+    this.file = { attachment: file, name };
+    return this;
+  }
+
+  /**
+    * Set the file of this attachment.
+    * @param {BufferResolvable|Stream} attachment The file
+    * @returns {MessageAttachment} This attachment
+    */
+  setFile(attachment) {
+    this.file = { attachment };
+    return this;
+  }
+
+  /**
+    * Set the name of this attachment.
+    * @param {string} name The name of the image
+    * @returns {MessageAttachment} This attachment
+    */
+  setName(name) {
+    this.file.name = name;
+    return this;
+  }
+
+  /**
+    * Set the file of this attachment.
+    * @param {BufferResolvable|Stream} file The file
+    * @param {string} name The name of the file
+    * @private
+    */
+  _attach(file, name) {
+    if (typeof file === 'string') this.file = file;
+    else this.setAttachment(file, name);
+  }
+
+  _patch(data) {
     /**
      * The ID of this attachment
      * @type {Snowflake}
      */
     this.id = data.id;
 
-    /**
-     * The file name of this attachment
-     * @type {string}
-     */
-    this.filename = data.filename;
-
     /**
      * The size of this attachment in bytes
      * @type {number}
      */
-    this.filesize = data.size;
+    this.size = data.size;
 
     /**
      * The URL to this attachment