Python version upgrade

[c-martinez]

Grlc currently supports Python 3.7, 3.8 and 3.9. but 3.7 has reached its end of life, with 3.11 being the current stable version.

[c-martinez]

Depending on the outcome of this, we should update dependencies such as Flask (#399)

[RinkeHoekstra]

Hi Carlos, all,

I think the key question is: what vulnerabilities exist in v3.7 libraries that grlc is using? In general, I'd be in favour of tracking at least the latest stable version of each library, and all security fixes. If that requires an update of the Python version, then so be it. We can't have vulnerabilities linger for too long.

One thing to consider is that AWS linux comes with Python 3.9 out of the box (but does offer 3.11 binaries as of this year).

Great to see that grlc is still alive and kicking!

[c-martinez]

Unless there are any objections, we will go for supporting 3.11,3.10, 3.9 (and 3.8 if possible & until next year)