feat(RichEmbed): add toJSON returning an api-compatible object

This backports:
PR: https://github.com/discordjs/discord.js/pull/3813
Commit: 4ec01ddef5

src/client/rest/RESTMethods.js

@@ -152,7 +152,7 @@ class RESTMethods {
       content = `${mention}${content ? `, ${content}` : ''}`;
     }
 
-    if (embed instanceof RichEmbed) embed = embed._apiTransform();
+    if (embed instanceof RichEmbed) embed = embed.toJSON();
 
     return this.rest.makeRequest('patch', Endpoints.Message(message), true, {
       content, embed, flags,

src/structures/RichEmbed.js

@@ -278,11 +278,10 @@ class RichEmbed {
   }
 
   /**
-   * Transforms the embed object to be processed.
+   * Transforms the embed to a plain object.
    * @returns {Object} The raw data of this embed
-   * @private
    */
-  _apiTransform() {
+  toJSON() {
     return {
       title: this.title,
       type: 'rich',

src/structures/Webhook.js

@@ -227,7 +227,7 @@ class Webhook extends EventEmitter {
       else options.files = files;
     }
 
-    if (options.embeds) options.embeds = options.embeds.map(e => new RichEmbed(e)._apiTransform());
+    if (options.embeds) options.embeds = options.embeds.map(e => new RichEmbed(e).toJSON());
 
     if (options.files) {
       for (let i = 0; i < options.files.length; i++) {

src/structures/interfaces/TextBasedChannel.js

@@ -147,7 +147,7 @@ class TextBasedChannel {
       else options.files = [options.file];
     }
 
-    if (options.embed) options.embed = new RichEmbed(options.embed)._apiTransform();
+    if (options.embed) options.embed = new RichEmbed(options.embed).toJSON();
 
     if (options.files) {
       for (let i = 0; i < options.files.length; i++) {