adl-support.tags

Application Description Language support - custom Selmer tags used
in generated templates.

add-tags

(add-tags)
FIXME: write docs

if-member-of-permitted

(if-member-of-permitted args context success failure)
If at least one of these `args` matches some group name in the `:user-roles`
of this `context`, return this `success`, else this `failure`.