Integrate gitlab auth

[r-scheele]

[Feature] /gitlab/login route requires cliend_id, and client_secret from gitlab - Users Settings > Applications the route returns an authorization code, which is redirected to a callback url in our application. verified, and then return an access token to the client. sample response:

{
  "access_token": "f50e2bf44ff901c2f619cef768f306f2561431413f0362a55fba42ec94fd1c12",
  "expires_in": 7200
}