feat: introducing rate-limiting on queries, mutations and most of the REST endpoints (HBE-111) (#46)

* feat: rate-limiting guard added and configured in app module

* feat: rate-limit annotation added in controllers and resolvers (query, mutation, not subscription)

* docs: added comments

packages/hoppscotch-backend/src/guards/throttler-behind-proxy.guard.ts

@@ -0,0 +1,10 @@
+import { ThrottlerGuard } from '@nestjs/throttler';
+import { Injectable } from '@nestjs/common';
+
+@Injectable()
+export class ThrottlerBehindProxyGuard extends ThrottlerGuard {
+  protected getTracker(req: Record<string, any>): string {
+    return req.ips.length ? req.ips[0] : req.ip; // individualize IP extraction to meet your own needs
+    // learn more: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-For#directives
+  }
+}