Files are being opened without encoding arg

[jacobtylerwalls]

Linters like pylint and ruff both discourage opening files without an encoding arg, which can cause problems when files written on one platform are opened on another. Because arches is a general library used cross-platform, this affects us.

One instance that came up was #11337 and was fixed, but there are dozens of other issues you can see if you turn on EncodingWarning (see PEP 597), which you don't need a linter for:

/Users/jwalls/prj/arches/arches/management/commands/load_ontology.py:84: EncodingWarning: 'encoding' argument not specified
  with open(config_file, "r") as f:
/Users/jwalls/prj/arches/tests/base_test.py:129: EncodingWarning: 'encoding' argument not specified

We have a few choices:

• add utf-8 encoding everywhere
• or, document that windows users should run python in utf-8 mode
• or, just want until Python 3.15 when utf-8 mode defaults on, but python has deferred things like this before, so there's no guarantee it will happen on schedule

Suggest adding explict utf-8 encoding and turning on EncodingWarning in CI and elevating it to an error. This will function like a linter without having to decide on adopting a linter like pylint or ruff in general.

(Finally, the django_storages backend allows setting default encoding apparently, but that's only a potential partial fix for that one backend and for files going through the storages interface.)