Guests created via Talk don't receive a welcome mail

Steps to reproduce:

• Create a talk conversation
• Enter a mail address in the share tab and select "Invite guest"
• In the modal add name and create the guest

Expected:

• The guest receives a mail that he was invited to a talk conversation and has the ability to reset the password

Current:

• No mail is send to the guest, so the person who created the guest needs to manually reach out to them and tell them to use the "Reset password" functionality to create the credentials

Additional:
Creating guests via file share is working correctly, the guest receive a mail. This is done inside the Hook.php: https://github.com/nextcloud/guests/blob/master/lib/Hooks.php

Start by comparing the Talk guest-creation path with the working invitation flow in lib/Hooks.php. Reproduce the steps in the issue and trace where the guest is created and where the welcome message is sent for file shares. Done means a guest created through Talk receives an invitation with password-reset instructions.