Update license tagging

[SebastianSchildt]

We are using an outdated way to declare the package licence, meanwhile Python supports an explicit SPDX identifier.

See this warning during build

#31 41.40 /tmp/build-env-sedgnv9l/lib/python3.10/site-packages/setuptools/dist.py:759: SetuptoolsDeprecationWarning: License classifiers are deprecated.
#31 41.40 !!
#31 41.40 
#31 41.40         ********************************************************************************
#31 41.40         Please consider removing the following classifiers in favor of a SPDX license expression:
#31 41.40 
#31 41.40         License :: OSI Approved :: Apache Software License
#31 41.40 
#31 41.40         See https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license for details.
#31 41.40         ********************************************************************************
#31 41.40 
#31 41.40 !!
#31 41.40   self._finalize_license_expression()

[aki1770-del]

Hi @SebastianSchildt — happy to take this one; it's self-contained.

The deprecated declaration is the classifier in kuksa-client/setup.cfg:

[metadata]
classifiers =
    ...
    License :: OSI Approved :: Apache Software License

The PEP 639 replacement is to drop that classifier and declare the SPDX
expression directly:

[metadata]
license = Apache-2.0

One thing worth flagging from the source: SPDX-expression support for the
license field landed in setuptools 77.x, but the build still pins
setuptools>=42 (kuksa-client/pyproject.toml). So the complete fix is the
SPDX expression plus bumping the build requirement to setuptools>=77 —
otherwise an older setuptools would treat Apache-2.0 as free-text and the
deprecation warning wouldn't actually clear.

Want me to open a PR for that (classifier removal + SPDX license +
build-requirement bump), or would you rather fold it into the broader SDK
packaging cleanup you mentioned in #53? Either way I'll keep it to that single
concern.

[SebastianSchildt]

Feel free to give fixing this a try. If this can be done in a contained way, and changing the config + bumping setuptools does the trick without bad side effects, I am all for it