fix(document): make Document class an event emitter to support defining documents without models in node

Fix #8272

Author: vkarpov15

lib/document.js

@@ -184,6 +184,10 @@ utils.each(
 
 Document.prototype.constructor = Document;
 
+for (const i in EventEmitter.prototype) {
+  Document[i] = EventEmitter.prototype[i];
+}
+
 /**
  * The documents schema.
  *

test/document.test.js

@@ -136,6 +136,8 @@ describe('document', function() {
       assert.ok(!myUserDoc.name);
       myUserDoc.name = 123;
       assert.strictEqual(myUserDoc.name, '123');
+
+      assert.ifError(myUserDoc.validateSync());
     });
   });