Add Github oAuth

[jeromehardaway]

Problem:

We only want people who are a part of Vets Who Code to have access to our AI Tool. In particular, we want those who are learners primarily to have access. This helps cut cost while also giving our troops premium access to a resource that we will add more resources to over time.

Solution:

Use Github Auth feature so that those only in the admin and troops category in the organization can get access to it.