docs: update entry point configuration from setup.cfg to pyproject.toml

[BorjaEst]

Fixes # (issue)

This pull request includes updates to the documentation to reflect changes in the configuration file format used for defining entry points. The most important changes are:

• doc/source/user/v2-api.rst: Updated instructions to use pyproject.toml instead of setup.cfg for defining entry points.
• doc/source/user/v2-api.rst: Changed code block examples from ini to toml format to match the new configuration file.# Description

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• This change is a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own 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

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[BorjaEst]

closes #195

[BorjaEst]

I cannot merge till the CI tests via tox pass.
There is a flake8 error, but I do not see the details (and pass for 3.11)