Fix false boolean configuration values

[bensynapse]

I run Live Tennis API.

A False default now uses Starlette's boolean parser when loading configuration. Previously, false remained a nonempty string and enabled optional behavior.

The tests cover environment variables and files, constructor defaults, invalid values, and HTTP header and storage failure behavior.

poetry run coverage run --omit="tests*" -m pytest passes all 132 tests on Python 3.9, 3.10 and 3.11. Black, mypy, flake8 --select F401 and coverage reporting also pass on all three versions. Twenty-one regression cases fail before the fix.

Fixes #311.

[agustin18]

Nice catch! Just wondering, maybe if default_value is not None: instead of if default_value: is simpler and cleaner here?

Because right now if someone passes default_value=0, it still skips casting since 0 is falsy, so it returns a string instead of an int.
With is not None, type(False) is already bool so Starlette parses the boolean, and it also handles 0 and other falsy defaults without needing the extra if default_value is False check.

[bensynapse]

Fixed in 93c53be. The condition now uses is not None, so zero defaults get their numeric type and False uses Starlette's boolean parser.
I removed the separate False branch and added ten cases for typed values and missing settings. All 142 tests pass on Python 3.9 to 3.11.
Black, mypy and the CI unused import check pass.