Notifying erp5 when a read occurs isn't as straightforward as sending a
request to erp5 when a data change occurs.

I think the reason for this is that OPC UA has the concept of subscriptions [1].
But as far as I understand it this concept only applies to important events
as data changes or OPCUA Events, but not to simple "read" or "browse"
requests. So to catch those requests and forward them to ERP5 we actually
need to adjust asyncua.

In this patch I picked a dirty-adhoc-monkey-patching approach, a cleaner
version may include defining a new custom ERP5Server, which inherits
from asyncua base Server class.

Because (AFAIK) it's not possible to track the read requests with the
subscription method, we may want to unify our forwarding system by dropping
the subscription approach and move everything to a patched InternalSession.

[1] https://documentation.unified-automation.com/uasdkhp/1.4.1/html/_l2_ua_subscription.html