These contain a channel key for a secret channel.
We also had to migrate the appservice-irc config to a secret.
Change-Id: I92c7cdf9679f65d9e655e22d690cef2e83180135
Configuring this one is a bit different from appservice-irc. Notably,
there's no way to give it a registration.yaml to overlay on top of a
config, se we end up using an init container with yq to do that for us.
Also, I had to manually copy the regsitration.yaml in synapse, from
/appservices/telegram-prod/registration.yaml to
/data/appservices/telegram-prod.jsonnet, in order to make it work with
the synapse docker start magic. :/
Otherwise, this is deployed and seems to be working.
Change-Id: Id747a0e310221855556c1d280439376f0c4e5ed6