direct message mail notification url error: opening the link gets "Room not found" or "User not found"

Description:

In the direct message mail notification, if you click on the "GO TO MESSAGE" link in email notification, you can get on weird page: the channel is displayed, but with "Room not found" and a big "icon-attention" sign + message ""No channel with name "xxx" was found"".

If you remove the "&msg=xxx" from the url, it works correctly.

It seems this param has been introduced in this commit

Steps to reproduce:

1. Send a direct message to someone offline
2. The offline user gets a mail with link to something like https://go.rocket.chat/room?rid=dQ2vCXopPYiCnWatN&mid=tfZdopsxPNdJeeXEM&host=rocket.esup-portail.org&path=channel/foobar?msg=xxxx
3. Clicking on the link gets you to the weird page (after login)

Reproduced on a CAS Rocket.Chat and a shib Rocket.Chat.

Expected behavior:

No error displayed

Actual behavior:

Server Setup Information:

• Version of Rocket.Chat Server: 3.10.5
• Operating System: Debian 10
• Deployment Method: tar
• Number of Running Instances: 1
• DB Replicaset Oplog: yes
• NodeJS Version: 12.20
• MongoDB Version: 4.4.3

Client Setup Information

• Desktop App or Browser Version: tested on both (and various browsers)
• Operating System: various

Additional context

Relevant logs:

Review the URL parameter change in commit 6fa7f3c368469db83c949b7edeaca7c23ab953fe, then trace the direct-message mail notification link and the route it opens. Reproduce with an offline direct-message recipient using the example URL, and confirm the corrected link opens the message without a "Room not found" or "User not found" error.