refactor(example): Ensure in the example that we only allow PS512 keys

docs/getting-started/event-log.md

@@ -214,6 +214,11 @@ static final ZUSTELLDIENST_BASE_URL = "https://zustelldienst.example.com";
 boolean verifySignature(SignedJWT securityEventToken, String keyId) {
   JWKSet jwks = JWKSet.load(ZUSTELLDIENST_BASE_URL + "/.well-known/jwks.json");
   JWK publicKey = jwks.getKeyByKeyId(keyId)
+
+  if (publicKey.getAlgorithm() != JWSAlgorithm.PS512) {
+    throw new RuntimeException("The key specified for signature verification doesn't use/specify PS512 as algorithm.")
+  }
+
   JWSVerifier jwsVerifier = new RSASSAVerifier(publicKey.toRSAKey());
   return signedJWT.verify(jwsVerifier);
 }