docs(document): add hydratedPopulatedDocs option info and other improvements to init() docs

Author: vkarpov15

lib/document.js

@@ -624,16 +624,17 @@ Document.prototype.toBSON = function() {
 };
 
 /**
- * Initializes the document without setters or marking anything modified.
+ * Hydrates this document with the data in `doc`. Does not run setters or mark any paths modified.
  *
- * Called internally after a document is returned from mongodb. Normally,
+ * Called internally after a document is returned from MongoDB. Normally,
  * you do **not** need to call this function on your own.
  *
  * This function triggers `init` [middleware](https://mongoosejs.com/docs/middleware.html).
  * Note that `init` hooks are [synchronous](https://mongoosejs.com/docs/middleware.html#synchronous).
  *
- * @param {Object} doc document returned by mongo
+ * @param {Object} doc raw document returned by mongo
  * @param {Object} [opts]
+ * @param {Boolean} [opts.hydratedPopulatedDocs=false] If true, hydrate and mark as populated any paths that are populated in the raw document
  * @param {Function} [fn]
  * @api public
  * @memberOf Document