Document known Trac limitations

[ulgens]

While I'm looking for potential cleanups in the repo, I learned that

• Trac doesn't support Python 3.12, so the latest Python version we can use is 3.11: [WIP] Switched to Python 3.12 #219 (comment)
• Trac only support psycopg2, we can't switch to psycopg - the newer versions: Upgrade to Psycopg 3 #223 (comment)

I think both are important issues that should be documented in a visible way. This may help the volunteers working on the repo and also contribute to the move-out of Trac discussions.

[ulgens]

My recommendation is to add this info to the readme file and add notes to the code where these versions/configs are set up.