Upgrade pyproject.toml to PEP 621

[reggna]

Right now, we get a lot of warnings running poetry check on a newer version of poetry:

The "poetry.dev-dependencies" section is deprecated and will be removed in a future version. Use "poetry.group.dev.dependencies" instead.
Warning: The "poetry.dev-dependencies" section is deprecated and will be removed in a future version. Use "poetry.group.dev.dependencies" instead.
Warning: [tool.poetry.name] is deprecated. Use [project.name] instead.
Warning: [tool.poetry.version] is set but 'version' is not in [project.dynamic]. If it is static use [project.version]. If it is dynamic, add 'version' to [project.dynamic].
If you want to set the version dynamically via poetry build --local-version or you are using a plugin, which sets the version dynamically, you should define the version in [tool.poetry] and add 'version' to [project.dynamic].
Warning: [tool.poetry.description] is deprecated. Use [project.description] instead.
Warning: [tool.poetry.readme] is set but 'readme' is not in [project.dynamic]. If it is static use [project.readme]. If it is dynamic, add 'readme' to [project.dynamic].
If you want to define multiple readmes, you should define them in [tool.poetry] and add 'readme' to [project.dynamic].
Warning: [tool.poetry.license] is deprecated. Use [project.license] instead.
Warning: [tool.poetry.authors] is deprecated. Use [project.authors] instead.
Warning: [tool.poetry.classifiers] is set but 'classifiers' is not in [project.dynamic]. If it is static use [project.classifiers]. If it is dynamic, add 'classifiers' to [project.dynamic].
ATTENTION: Per default Poetry determines classifiers for supported Python versions and license automatically. If you define classifiers in [project], you disable the automatic enrichment. In other words, you have to define all classifiers manually. If you want to use Poetry's automatic enrichment of classifiers, you should define them in [tool.poetry] and add 'classifiers' to [project.dynamic].
Warning: [tool.poetry.homepage] is deprecated. Use [project.urls] instead.
Warning: [tool.poetry.repository] is deprecated. Use [project.urls] instead.
Warning: Defining console scripts in [tool.poetry.scripts] is deprecated. Use [project.scripts] instead. ([tool.poetry.scripts] should only be used for scripts of type 'file').

Once the long list of pull requests has been integrated, we should consider updating pyproject.toml to be compliant with PEP 621. This however, requires poetry to be updated to at least 2.0.0 (which would require an upgrade on the cloud @Tigge).

Migrating should be easy using poetry config --migrate. I'm attaching a diff from the live branch.

pep_621_pyproject.patch