Add rate limiting and improve e2e testing workflow

- Add express-rate-limit to custom endpoints for security:
  - /introspect: 100 requests per 5 minutes
  - /fakeupstreamauth/*: 20 requests per minute
  - Static files: 25 requests per 10 minutes
- Add automated e2e testing npm scripts using concurrently:
  - npm run test:e2e:integrated: Auto-starts server and runs test
  - npm run test:e2e:separate: Auto-starts both servers and runs test
- Update README with automated testing approach documentation
- Update docs/streamable-http-design.md with current file structure
- Remove redundancy in README e2e testing documentation
- Verified: All tests, linting, and e2e scripts pass with rate limiting

package.json

@@ -20,7 +20,9 @@
     "lint": "eslint src/ auth-server/",
     "test": "NODE_OPTIONS=--experimental-vm-modules jest",
     "test:integrated": "AUTH_MODE=integrated npm test",
-    "test:separate": "AUTH_MODE=separate npm test"
+    "test:separate": "AUTH_MODE=separate npm test",
+    "test:e2e:integrated": "concurrently --kill-others --success first \"npm run dev:integrated\" \"sleep 4 && ./scripts/test-integrated-e2e.sh\"",
+    "test:e2e:separate": "concurrently --kill-others --success first \"npm run dev:with-separate-auth\" \"sleep 6 && ./scripts/test-separate-e2e.sh\""
   },
   "devDependencies": {
     "@eslint/js": "^9.15.0",
@@ -42,6 +44,7 @@
     "cors": "^2.8.5",
     "dotenv": "^16.4.7",
     "express": "^4.21.2",
+    "express-rate-limit": "^8.0.1",
     "raw-body": "^3.0.0"
   },
   "overrides": {