fix: package.json & yarn.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-KOA-10944994

Author: snyk-bot

package.json

@@ -33,7 +33,7 @@
     "ldap"
   ],
   "dependencies": {
-    "koa": "^1.0.0",
+    "koa": "^3.0.1",
     "koa-buddy": "^0.1.0",
     "koa-router": "^5.1.2",
     "koa-swig": "^2.0.0",