Defines a private `in-staging.softwareheritage.org` dns subdomain.
in-staging as in a contraction of:
- in-house
- internal
- and synonym of "private" (in this context)
Feel free to provide a better/more suitable name, i'm bad at naming.
The public facing part (`staging.softwareheirtage.org`) needs to be addressed outside of puppet within swh's gandhi account.
Related T1876