This configuration option reflects a new feature from the unreleased
spacecookie version allowing to customize the address spacecookie will
listen on (e. g. "::1" to bind on link-local addresses only). We will
not use this feature in the future, since the configuration option of
spacecookie naturally only has an effect if we don't use socket
activation (and spacecookie sets up its own socket), but having the same
functionality in the service seems like a good idea.
We can luckily emulate this behavior with socket activation as well.
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