[deploy] Move daily backup CronJob into a separate file

See merge request !2

This backup is optional.

Now logilab/cubicweb:dev use a cubicweb compatible with ldap3>=2

And bw compat has been dropped in cubicweb 3.27

Otherwise running them in parallel may fail.

Followup eee88e429e72: method should be named "get_concerned_by"

To allow larger uploads.

We don't need it anymore because bfss has been moved to /etc/cubicweb.d/fresh/bfss

We use bfss to store upload of (mostly) pdf files.
Add a persistent volume claim and mount it in /var/lib/cubicweb/instances/fresh/bfss
To make this work with previous instance we have to rename the instance to "fresh".

In extentities generator, extid is cwuri from database which is a text field.
So in python3 exteid2eid[extid] wasn't matching anything because extid was bytes.
Use text extid instead.

Kubernetes can set a mode using "defaultMode" but cannot mount the file with
other uid than root.
So we have to mount the secret and copy it with good mode and ower in
/etc/cubicweb.d/fresh/cwclientlibrc...