Nothing on the backup path looks at restores. A Plan creates its
BackupJobs on schedule, and the BackupJob reconciler dispatches them to
their driver whatever else is happening to the application. For CNPG that
is not merely a backup of a half-restored state: every BackupJob reconcile
re-applies the Cluster's barman plugin, and on a cluster under an in-place
restore it can land after the chart has re-rendered the Cluster with its
new serverName and put it back on the source's. The restored cluster then
archives onto the source's WAL prefix and its recovery fails with "WAL
archive check failed ... Expected empty archive". This was reproduced
with a backup triggered a few seconds after an in-place restore, and an
hourly plan overlaps a restore of up to thirty minutes about half the
time.

A BackupJob that has not started yet now waits while a non-terminal
RestoreJob in its namespace writes into the same application, resolved
as the drivers resolve it: the Backup's applicationRef, with the target's
kind and name when a targetApplicationRef is set, and the target's API
group only when it names one. A RestoreJob whose Backup is gone holds
nothing, since the restore controller fails it on its next pass.
options.targetNamespace is honoured only for a Backup taken by the Velero
strategy, the one driver that reads it; the CNPG and Job-based drivers
ignore the option and restore in place, so their restores hold whatever
it says.

The held job stays Pending with a Ready=False RestoreInProgress condition
naming the restore and is requeued, rather than failed, so a scheduled run
still happens once the restore ends. A failed write of that status is
returned, so the manager retries it. When the restore ends the condition is
removed before the job starts, since it would otherwise read "waiting"
until the driver next writes Ready, which for a healthy run is when the
backup completes. A run that has already started is left alone: its driver
owns state the gate would strand.

Assisted-by: LLM
Signed-off-by: Mattia Eleuteri <[email protected]>
(cherry picked from commit af8cf74)