bump version to 7.99.0

bump version to 7.99.0

use a pre-release like version as we got some breaking changes
planned for access control, so might be nice to get (most of) them in
a 8.0.0 for simpler versioned  dependencies (>= 8~), but it's also
just a bit of an experiment to see how doing such things plays out,
in the end we can cope with whatever versioning for dependency as bug
fixes might make it necessary to have a more specific version
boundary anyway.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>