Revoking a host now unassigns its instances instead of being refused
while it has any, and removes its system metrics.
Approving and revoking no longer force a save. Hosts are saved by
autosave and on exit like everything else, which also removes the
approving state from pairing requests.
The approval code and link are logged as warnings so they show up in
the systemd service, which only prints warnings and above. The pairing
limits are now the controller.host_pairing_timeout and
controller.host_pairing_max_pending config values, 0 removes the limit.
Subscribers take an optional permitted function, used for the pairing
requests instead of overrides in a subclass.
The installer only writes the controller URL and host name. Running the
host requests to join the cluster if it has not been approved yet, or if
the controller no longer accepts its token, and waits until an admin
approves it. Once approved it saves its id and token and starts as
normal. A rejected host exits with code 8.
clusteriohost run --user-token approves the host right away with the
token of a user allowed to approve hosts. The token is not saved.
This moves the pairing client into the host package, where it uses the
same certificate setup as the host's connection to the controller, and
removes --no-pair and the rerun handling from the installer.
Danielv123