Linkedin Login

Linkedin_Login.js

STEPS:
1.- Create an app:
in linkedin: https://www.linkedin.com/developers/apps

2.- Create your linkedin login URL:
Fill the following URL with your developer information: https://www.linkedin.com/oauth/v2/authorization
example with response_type, client_id, redirect_uri, state:
https://www.linkedin.com/oauth/v2/authorization?response_type=code&client_id=86zig0sfofozk1&redirect_uri=https://localhost:8443/pro&state=aRandomString

3.- Get the user code from linkedin:
redict the user to this URL, after the user completes the linkedin login,
is going to be redirect to the `redirect_uri` URL you defined in the URL
(this URL have to match with any of the ones you have in your linkedin developer account in `Redirect URLs`).
the redirect URL is going to have a code= from linkedin like this:
https://localhost:8443/pro?code=AQRM1TNl6EFx7Y4KuqRvRcmI7Y2PS0qMHX_AKeFoIxKbho0NLhB3D-1KSyINsgur9WvM_mufdsnkpkOXeNZQwYz2Ww05JRGH6q-rRKjISFt-Qk_sHhjn7L8gDBVaBcZVD27-Z4D-Rz-1bq96jq3Q0tQHKvAF_DNxwXB6439_UQvjCvtGkRNZZCasugdayQ&state=aRandomString
copy this code.

4.- Get the user token from linkedin:
In orther to get the user token you need to make a POST request with the folling information
as Params client_id, client_secret, grant_type, redirect_uri, code 
like this: 
https://www.linkedin.com/oauth/v2/accessToken?client_id=86zig0sfofozk1&client_secret=N80cs7CMtQPgNCmV&grant_type=authorization_code&redirect_uri=https://localhost:8443/pro&code=AQQud3mML44FbdYgDZpiDGqlNZNpK1pXgJ7LPBaECvcNjfV33kPRUTD2eU_Gk1LJB2KKCcQRuAvPChvy8ibC8L_PaELJLOFJBF7Grt-CUtZxwIOFrvy7OOXtvO2swuAr3OkZyYyGtQ9c1tnE2vgaa07XCTm_2rvLhFUaiFLUToxr79tM1twXuzxWQNPgOw
and in the Headers of the POST request this: Content-Type: "application/x-www-form-urlencoded"
Linken is going to response with a `access_token`

5.- Use the access token to get the user information:
Make a GET request to: https://api.linkedin.com/v1/people/~:(first-name) 
Note that you can ask for more things not only the first name.
In the Headers: Authorization: Bearer AQUUcZlT5YwBBpZzq0xyctUR1k8tyENmdX5_kJBd1YiqlJaZAGk38dcLBF8N2Bi2YnprQA-mi8z-br22BqjOsQbljGTi5TqH9K6ZDHl9UjHl2QVziLMq9o9GOaP-WbwXZT6lAXjYbwEHHfQmB6r0Bq27SdeOuqsHSEykrTyTtLNfV7EgVcEhGTSTXVEr9iyJkzVH9fvx_I9hZvuFyLxi-rT1ssRwp_uWe3IBcSueGJHb0x7JAI2As3Q2PP2WIEldAEGWv1JzokLkTr1G2GJAzL-6AQOjWrRa2gU0ghga3aJWFGjdvQCDDHS3oa7ETNDpuei8PwuOfau0f68PzV9zoE_i2Q21rQ
Add the token in the Authorization headers as a Bearer.

LINKS: 
https://medium.com/@ellesmuse/how-to-get-a-linkedin-access-token-a53f9b62f0ce
https://www.linkedin.com/developers/
https://developer.linkedin.com/docs/signin-with-linkedin#