We're casting everything it `int`, but since Jinja templates are
involved, these values end up as strings anyway.

Doing `| int | to_json` is good, but we should only cast numbers to
integer, not empty strings, as that (0) may be interpreted differently
by Synapse.

To turn of auto-tuning, one is possibly supposed to pass empty strings:

> This option defaults to off, enable it by providing values for the sub-options listed below.

It could be that `0` is also considered "no value provided", but I
haven't verified that.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3017