Update Email Notifications to use matrix.to links

[hanthor]

Having direct links to element web does not work on mobile. It should link to a matrix.to link in the message to the users can open email notifications on their phone

[H-Shay]

So it looks like this is the code to generate the links in the email notifications:

synapse/synapse/push/mailer.py

Lines 823 to 846 in 1294d10

	def _make_notif_link(self, notif: EmailPushAction) -> str:
	"""
	Generate a link to open an event in the web client.
	Args:
	notif: The notification to generate a link for.
	Returns:
	A link to open the notification in the web client.
	"""
	if self.hs.config.email.email_riot_base_url:
	return "%s/#/room/%s/%s" % (
	self.hs.config.email.email_riot_base_url,
	notif.room_id,
	notif.event_id,
	)
	elif self.app_name == "Vector":
	# need /beta for Universal Links to work on iOS
	return "https://vector.im/beta/#/room/%s/%s" % (
	notif.room_id,
	notif.event_id,
	)
	else:
	return "https://matrix.to/#/%s/%s" % (notif.room_id, notif.event_id)

It looks like in some cases matrix.to links are generated, although not in the case where the app_name is "Vector" so perhaps that is the problem.