API v3 Rate Limiter (#12117)

* simplify ip address management by using the trust proxy express option

* add setupExpress file

* fix redirects middleware tests

* fix lint

* short circuit the ip blocking middleware

* basic implementation with ip based limiting

* improve logging

* upgrade apidoc

* apidoc: add introduction section

* fix lint

* fix tests

* fix lint

* add unit tests for rate limiter

* do not send retry-after header when points are available

* automatically fix lint

* fix more lint issues

* use userId as key for rate limit when available

package.json

@@ -60,6 +60,8 @@
     "paypal-ipn": "3.0.0",
     "paypal-rest-sdk": "^1.8.1",
     "ps-tree": "^1.0.0",
+    "rate-limiter-flexible": "^2.1.7",
+    "redis": "^3.0.2",
     "regenerator-runtime": "^0.13.5",
     "remove-markdown": "^0.3.0",
     "rimraf": "^3.0.2",