frontend, doc: use the same repofile for all Fedora versions including Rawhide
    
    Fix #639
    See PR#492
    
    With this patch we will generate the same `baseurl` for all Fedora
    versions. Therefore there won't be special `fedora-rawhide-$basearch`
    for Rawhide but rather `fedora-$releasever-$basearch`.
    
    When additionally configuring
    
        CHROOT_NAME_RELEASE_ALIAS = {
    	"fedora-35": "fedora-rawhide",
        }
    
    The following URL alias will start to work
    http://127.0.0.1:5000/coprs/frostyx/rawhide-repos/repo/fedora-35/
    even though technically, there is no `fedora-35-*` chroot in the
    database.
    
    Thanks to this, both
    
        dnf copr enable frostyx/rawhide-repos --releasever=35 --hub=localhost
        dnf copr enable frostyx/rawhide-repos --releasever=rawhide --hub=localhost
    
    works as expected and enable the repository correctly. The only
    missing piece is that the following command works
    
        dnf install foo --refresh --releasever=rawhide
    
    but this one doesn't
    
        dnf install foo --refresh --releasever=35
    
    AFAIK this is not a regression so it probably shouldn't be a
    blocker. But I am for solving it now, if you agree. Do you have any
    suggestions what would be ideal solution to link `fedora-35-*` chroots
    on the backend to `fedora-rawhide-*`? Maybe some mod_rewrite thingy?