WMAgent v2.3.9 validation

[amaltaro]

Impact of the new feature
WMAgent

Is your feature request related to a problem? Please describe.
By-monthly task

Describe the solution you'd like
We need to release a new WMAgent stable version in Jan/2025, so this issue is meant to keep track of the full validation activity to be carried out in the first weeks of January, once we have a final 2.3.9 tag (on top of stable central services in 2.3.8).

In addition to the validation results, WMAgent release notes and the validation check-list document need to be created as well.

Describe alternatives you've considered
None

Additional context
None