GITHUB_OAUTH

On Frontend
- User clicks Login With Github Button.
- We redirect user to https://github.com/login/oauth/authorize with client_id, redirect_uri and scope as query params.
- Example
```
https://github.com/login/oauth/authorize?scope=user:email&client_id=<CLIENT_ID>&state=<state>
```
- Once user allows access github redirect back us to supplied redirect_uri with code as query parameter.
- Example
```
https://linklet-api.now.sh/api/github/callback?code=34f137a0ea8d9306b7d9&state=JDTzqABd3XYTj8s6GUlO
```
  I used https://linklet-api.now.sh/api/github/callback this as redirect_uri before.
- Then we need to send this code to our backend.

On Backend

Then we use this code along with our clientId, clientSecret to obtain access_token and refresh_token. i.e send post request as shown below on backend side.

Example in node.js

  fetch('https://github.com/login/oauth/access_token', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    Accept: 'application/json',
  },
  body: JSON.stringify({
    clientId,
    clientSecret,
    code,
  }),
})
  .then(data => data.json())
  .then(json => {
    console.log(json.access_token)
    console.log(json.refresh_token)
    // use this `access_token` to fetch user profile details using this URL https://api.github.com/user?access_token=<access_token>
   });

In this we use our previously authenticated access_token to get user profile deatails from that service or make other API calls to that service
We may store user data in database
This ends creating user in database and we may create user session for our backend in order to keep track of authenticated user for our backend

We may or may not store access_token or refresh_token in our database.

If we only want to autheticate users then no need of storing them.
If we want to interact with that service later for eg: In case of facebook we want post something on behalf of user or in case of github create a pullrequest on behalf of user etc.. Then we use this access_token to access that service on behalf of that user.

BTW access_token is shortlived i.e it expires after sometime for security reasons. So again we need to ask user to login with that service that would be bad UX, so OAUTH providers provide an easy way i.e refresh_token. We use this token along with our ClientSecret to obtain new access_token and new refresh_token form that service.

This is what i understood.

pbteja1998/readme.md