The "web" group is moved to webserver-core, as a part of the effort
to sync all our roles nginx configurations. This group is intended
to be used by all web-related resources needing access sharing.
The "one domain name, one account" for static sites content works well,
so we adopt it in webserver-alkane.
Units adopted in webserver-alkane will be moved from webserver-legacy
to avoid duplication.
Ref T1828