[ANNOUNCE] dbus-broker v28

[David Rheinsberg]

Hi

We just released v28 of dbus-broker. This is again a bugfix release
with many fixes all over the place. All users are recommended to
upgrade!

https://github.com/bus1/dbus-broker/releases/tag/v28

## CHANGES WITH 28:

* Further improvements to the service activation tracking. This better
tracks units in systemd and closes some races where a repeated
activation would incorrectly fail.

* Fix a crash where duplicate monitor matches would be incorrectly
installed in the broker.

* Clear the ambient capability set to harden against possible exploits.

* A couple of bug-fixes in the utility libraries, and static
dependencies of the broker.

Contributions from: David Rheinsberg

- Dußlingen, 2021-03-17