Turnserver TLS certificate not checked

Steps to reproduce

1. Set up a turn server with domain turn.server.tld
2. In the turn server configuration, specify an TLS certificate to be used from a different domain e.g. different.domain.tld
3. Enter the turn/stun server domain turn.server.tld to nextcloud talk settings in your nextcloud instance.
4. Start a call via nextcloud talk app.

Expected behaviour

The call should not start as we have a certificate mismatch.

Actual behaviour

The call is initiated without error.

Talk app

android v8.2.0

Custom Signaling server configured:
no

Custom TURN server configured:
yes, coturn

Custom STUN server configured:
yes, coturn

Browser

Microphone available:
yes

Camera available:
yes

Operating system:
Ubuntu 20.04.1 LTS

Browser name:
Chromium

Browser version:
Chromium Version 88.0.4324.96 (Official Build) snap (64-bit)

Server configuration

Operating system
Debian 10

Web server:
Nginx

Database:
Maria 10.5.8

PHP version:
7.4.14

Nextcloud Version:
20.0.5

Start with the Android Talk TURN/STUN connection path described in the reproduction steps and trace how the configured server certificate is validated. Reproduce the mismatched-certificate setup, then verify that the call is rejected with an error rather than initiated.