Update value of User-Agent HTTP request header used by listers
That HTTP header value will now contain the lister name but also a link to our contact form in order for sysadmins to easily reach us if needed.
The following template is used to generate it:
"Software Heritage <lister_name> lister v (+https://www.softwareheritage.org/contact)"
Depnds on !311 (closed)
Migrated from D8523 (view on Phabricator)