chore: Upgrade to Python 3.9

[l0b0]

Enabler

So that we can use the most recent language features, we want to upgrade Python from 3.8 to 3.9.

Acceptance Criteria

• CDK Lambda functions use the Python 3.9 Docker image
• .python-version has version 3.9.0 or later
• pyproject.toml limits Python version to between 3.9 and 3.10 (exclusive)
• CI workflows use Python 3.9

Additional context

We need to wait for AWS to support Python 3.9 Lambda functions.

Tasks

• ...
• ...

Definition of Ready

• This story is ready to work on, according to the team's definition

Definition of Done

• This story is done, according to the team's definition

[billgeo]

Hey @l0b0 did you do any work on this this sprint. Or did you close if for another reason?

[l0b0]

I finished this, but forgot to link the PR.

[billgeo]

Cool. Thanks. Just retrospectively adding an estimate to make the sprint reporting work. 😄