feat: Refactor OAuth management to manage Logout

[taorepoara]

About this PR

OAuth2 management with a controller. This ease custom implementation for the OAuth2.

Technical highlight/advice

Some elements are keep but deprecated in order to migrate to the controller system at the next breaking release.

How to test my changes

In a LenraApplication sub widget, you can get the LenraApp instance and logout with the next code:

LenraApp.of(context).oauth2Controller.logout();

Checklist

• I didn't over-scope my PR
• My PR title matches the commit convention
• I did not include breaking changes
• I made my own code-review before requesting one

I included unit tests that cover my changes

• 👍 yes
• 🙅 no, because they aren't needed
• 🙋 no, because I need help

I added/updated the documentation about my changes

• 📜 README.md
• 📕 docs/*.md
• 📓 docs.lenra.io
• 🙅 no documentation needed