fix: support youtube watch links as preview links

(cherry picked from commit f63a4a44a2)

frontend/src/utils/index.js

@@ -696,7 +696,6 @@ export const escapeHTML = (text) => {
 		'"': '"',
 		"'": ''',
 		'`': '`',
-		'=': '=',
 	}
 
 	return String(text).replace(

lms/lms/doctype/lms_course/lms_course.py

@@ -47,7 +47,9 @@ class LMSCourse(Document):
 			).save(ignore_permissions=True)
 
 	def validate_video_link(self):
-		if self.video_link and "/" in self.video_link:
+		if self.video_link and "watch?v=" in self.video_link:
+			self.video_link = self.video_link.split("watch?v=")[-1]
+		elif self.video_link and "/" in self.video_link:
 			self.video_link = self.video_link.split("/")[-1]
 
 	def validate_status(self):