feat: Remove AuthModel to only use OAuthModel

[jonas-martinez]

About this PR

Linked to lenra-io/server#399

Following the issue referenced above, I have done a rework on the authentication process on client-common. This rework involves removing the AuthModel which was an old class used for handling authentication. I regrouped everything in the OAuthModel which is the new Model for handling authentication on Lenra. This also simplifies the authentication checks on the backoffice as you can see on the following pull request : lenra-io/backoffice#123.

How to test these changes

You can test these changes by using the backoffice's PR referenced above and using this branch as the client-common dependency in the backoffice. Then, run the latest server version and make sure that you have created an oauth client using the oauth documentation in the docs folder of the server.

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