update license-related keys in pyproject.toml

[sjvrijn]

Checklist before requesting a review

• I have read the contribution guidelines
• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• All user facing changes have been added to CHANGELOG.md

Type of change

Please delete options that are not relevant.

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
  This would be technically be breaking for anyone using build tools that don't support PEP 639, although I don't expect it to be an actual problem.

List of related issues or pull requests**

Refs:

• Update license keys in pyproject.toml #706

Describe the changes made in this pull request

pyproject.toml:

• Removed license classifier from the classifiers list (no longer supported in new format, and wasn't properly configured anyway 🙈)
• Added license-files key, with NOTICE only appearing for Apache license
• Updated license key to specify SPDX identifier of selected license, omit key if license is "Other"

MANIFEST.in:

• Only include NOTICE for Apache license

Instructions to review the pull request

Install the requirements

<install uv>
cd $(mktemp -d --tmpdir py-tmpl-XXXXXX)

Create a new package using the template, selecting the various license options

uvx copier copy \
    https://github.com/nlesc/python-template test_package \
    --vcs-ref pep-639

TIP: after filling it in for the first time, save the .copier-answers.yml file somewhere else, remove the line with the license answer, and specify it as the --data-file, so you only have to answer the license question in future iterations:

uvx copier copy \
    https://github.com/nlesc/python-template test_package \
    --vcs-ref pep-639 \
    --data-file .copier-answers.yml

Check that pyproject.toml and MANIFEST.in are rendered correctly/nicely

# Create a local environment to test your generated package locally
cd test_package
less pyproject.toml
less MANIFEST.in
uvx --from build pyproject-build --installer uv

# go back to folder in /tmp, clear generated package and try again with a new license option
# cd .. && rm -rf test_package