Add toJSON methods (#1859)

* tojson things

* fix client

* ignore private properties

* remove extra property descriptors

* handle primitive flattening

* remove unused import

* add toJSON to collections

* reduce stateful props

* state

* allow custom prop names when flattening

* fix client

* fix build

* fix flatten docs

* remove guild.available, cleanup permissions, remove arbitrary id reduction

* fix util import

* add valueOf as needed, update member props

* fix incorrect merge

* update permissionoverwrites and permissions

remove serialization of permissions in PermissionOverwrites#toJSON.
change Permissions#toJSON to serialize permissions, by default excluding
admin checks.

* change Permissions#toJSON to return the primitive

* Permissions#toJSON explicitly return bitfield

src/util/Util.js

@@ -12,6 +12,41 @@ class Util {
     throw new Error(`The ${this.constructor.name} class may not be instantiated.`);
   }
 
+  /**
+   * Flatten an object. Any properties that are collections will get converted to an array of keys.
+   * @param {Object} obj The object to flatten.
+   * @param {...Object<string, boolean|string>} [props] Specific properties to include/exclude.
+   * @returns {Object}
+   */
+  static flatten(obj, ...props) {
+    const isObject = d => typeof d === 'object' && d !== null;
+    if (!isObject(obj)) return obj;
+
+    props = Object.assign(...Object.keys(obj).filter(k => !k.startsWith('_')).map(k => ({ [k]: true })), ...props);
+
+    const out = {};
+
+    for (let [prop, newProp] of Object.entries(props)) {
+      if (!newProp) continue;
+      newProp = newProp === true ? prop : newProp;
+
+      const element = obj[prop];
+      const elemIsObj = isObject(element);
+      const valueOf = elemIsObj && typeof element.valueOf === 'function' ? element.valueOf() : null;
+
+      // If it's a collection, make the array of keys
+      if (element instanceof require('./Collection')) out[newProp] = Array.from(element.keys());
+      // If it's an array, flatten each element
+      else if (Array.isArray(element)) out[newProp] = element.map(e => Util.flatten(e));
+      // If it's an object with a primitive `valueOf`, use that value
+      else if (valueOf && !isObject(valueOf)) out[newProp] = valueOf;
+      // If it's a primitive
+      else if (!elemIsObj) out[newProp] = element;
+    }
+
+    return out;
+  }
+
   /**
    * Splits a string into multiple chunks at a designated character that do not exceed a specific length.
    * @param {string} text Content to split