Add docs and dependencies for Azure DevOps provider

[szecsip]

This PR encompass two critical aspects: documentation improvements and Python requirement specifications about Azure DevOps provider. These enhancements aim to streamline the integration process and ensure seamless functioning of the Azure DevOps provider.

[mrT23]

I am hesitant about adding the azure packages to requirements.txt

The requirements file is getting bigger and bigger, while most people probably won't use these specific packages

@okotek any thoughts about this ? do you know a way to enable people do install packages on-demand, instead by default ?

[szecsip]

I am hesitant about adding the azure packages to requirements.txt

The requirements file is getting bigger and bigger, while most people probably won't use these specific packages

@okotek any thoughts about this ? do you know a way to enable people do install packages on-demand, instead by default ?

I think in the future we have to create pip installable package, and control (all) providers dependencies install like pip install pr-agent[azure]. (for example with pyproject project.optional-dependencies configuration)