support Python 3.12?

[jGaboardi]

Depending on whether splot is archived or not, we need to keep up with modern CI practices an supported Python versions.

• add Python 3.12 support
• drop Python 3.9 support
• xref:
  • modernize infra - pyproject.toml [2024-07-08] #181
  • testing against Python 3.12 across federation pysal#1340

[martinfleis]

I would certainly not archive it anytime soon. We first need to move all the functionality elsewhere and provide a decent transition period. So bare maintenance is needed here.

[jGaboardi]

I would certainly not archive it anytime soon. We first need to move all the functionality elsewhere and provide a decent transition period. So bare maintenance is needed here.

Agreed. This issue is merely to get something on record as a point-in-time decision that we decided on doing "something."

And we should probably have discussion here in this issue on how to handle the transition.