Add OAuth2 Authorization and Callback rest endpoints

URL generation for OAuth2 authorization and the subsequent login
callback are handled at the backend API. While this can be done
client side, the credentials are better managed entirely on the
server side.

packages/cli/package.json

@@ -78,9 +78,11 @@
         "basic-auth": "^2.0.1",
         "body-parser": "^1.18.3",
         "body-parser-xml": "^1.1.0",
+        "client-oauth2": "^4.2.5",
         "compression": "^1.7.4",
         "connect-history-api-fallback": "^1.6.0",
         "convict": "^5.0.0",
+        "csrf": "^3.1.0",
         "dotenv": "^8.0.0",
         "express": "^4.16.4",
         "flatted": "^2.0.0",