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/gql-throttler.guard.ts

@@ -0,0 +1,12 @@
+import { ExecutionContext, Injectable } from '@nestjs/common';
+import { GqlExecutionContext } from '@nestjs/graphql';
+import { ThrottlerGuard } from '@nestjs/throttler';
+
+@Injectable()
+export class GqlThrottlerGuard extends ThrottlerGuard {
+  getRequestResponse(context: ExecutionContext) {
+    const gqlCtx = GqlExecutionContext.create(context);
+    const ctx = gqlCtx.getContext();
+    return { req: ctx.req, res: ctx.res };
+  }
+}