feat: add GitLab token support to avoid API rate limits

[vuillaut]

Adds gitlab_authorization parameter throughout the call chain. A single token works for gitlab.com and any self-hosted GitLab instance (salsa.debian.org, gitlab.in2p3.fr, etc.).
Three ways to provide the token (priority order):

• somef describe --gitlab_token
• SOMEF_GITLAB_TOKEN environment variable
• somef configure (stored in ~/.somef/config.json)

[vuillaut]

I could test the feature on a private gitlab.in2p3.fr repository

If you would like an integration test, you will need to test with a gitlab repository where you can create a token and add it as github variable for the tests.

[dgarijo]

Thanks @vuillaut,

• Can you please target the dev branch? That is the latest one.
• Do we need to propagate the authorization to all the retriever methods? I think we can send the corresponding authorization based on whether we are on GitLab or GitHub. Maybe we can even read it directly from the configuration object when needed.

To be consistent, we should probably keep the third option only. It's the one we have for GitHub. But I like the first option too, so I am keen to keep that one.

[vuillaut]

You are absolutely right about the consistency, I should have looked more closely at this.

The authorization could be read from config indeed, that would simplify the code a lot. But to stay consitent, I would need to also simplify the github functions to not pass github auth and simply read it from config as well. Is that ok ?