(RUF012) Fixed mutable class Defaults- Task 4

[drona-gyawali]

Part of #10196
NOTE: These are NOT automated changes, they are done by hand

• Prevents accidental modifications of mutable class attributes at the instance level.
• Aligns with project style guidelines enforced by Ruff.

Technical

• Updated mutable class attributes in 6 files to use typing.ClassVar for clarity and correctness.
• Added ClassVar annotations to mutable class attributes to ensure they are treated as class-level attributes.
• Ensured proper type hints for clarity and type safety.

Testing

Ran ruff check --select RUF012 to confirm no further warnings.

Screenshot

N/A

Stakeholders

@RayBB

[RayBB]

Looks great to me.
Now we need staff to review/merge.

[RayBB]

@drona-gyawali I looked at this with Drini and we realized we probably don't want all these values to be mutable.
Can you review and add non-mutable options to this and the other PRs (unless it needs to be mutable).

See https://docs.astral.sh/ruff/rules/mutable-class-default/

[drona-gyawali]

I'll make the necessary changes and let you know once they're ready for review.

[drona-gyawali]

Hi @RayBB , I made changes in 4 files, but in this PR, there are 6 files, and I left two files unchanged: tests/solr/test_update.py and tests/solr/updater/test_work.py because I was a bit confused about whether to keep mutable defaults or immutable defaults. As of now, these two files are following mutable defaults, but I am unsure what to do. Please guide me.

[RayBB]

@drona-gyawali it looks like a good start.
I see that Mapping is deprecated so try MappingProxyType instead.

As far as the ones if you're not sure if they're mutable I'd say:

1. Check if they're being changed somewhere, if so point to where and we can look closer. They probably shouldn't be changed.
2. You can also try just changing them to be immutable and maybe mypy will complain if they're not.