Switch to license expression in pyproject.toml #293
Description
The libraries in this repo (including the template and examples) use trove classifiers to specify their license. This is now deprecated, so we should switch to using the project.license field in pyproject.toml. The license specifier would be Apache-2.0.
This could be addressed in a single PR that updates all libraries. The libraries don't need to be released in the same PR, the updated metadata would just be ready to be published in their next release. Alternatively, maybe one PR per CODEOWNER would be better. The charmlibs-maintainers owned libraries could be released immediately with a post-release version.