Replace deprecated python setup.py develop with pip install -e . in extension development docs

[cgoldshtein]

Problem: CKAN's official extension development workflow uses python setup.py develop, which is deprecated and will stop working by October 2025.

Current (deprecated):

python setup.py develop

Modern replacement:

pip install -e .

Error developers see:

Please avoid running setup.py and develop. Instead, use standards-based tools like pip or uv. By 2025-Oct-31, your builds will no longer be supported.

What needs updating:

Extension development documentation

Extension tutorial/cookiecutter template

Docker development scripts

Any CKAN CLI tools using setup.py develop

Impact: Affects all extension developers. Will become a breaking change in late 2025.

References:

https://github.com/pypa/setuptools/issues/917

[Zharktas]

https://github.com/ckan/ckan/issues/8382 related discussion in general how extensions and ckan itself should be installed in the future.

[fpichardom]

When I use ckan config-tool in CKAN 2.11.3 I get the warning: ckan/ckan/cli/cli.py:7: UserWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html. The pkg_resources package is slated for removal as early as 2025-11-30. Refrain from using this package or pin to Setuptools<81. from pkg_resources import iter_entry_points

I'm not sure if this is related to the issue or if it requires a new one.