make the webhook expire days longer

[kinderyj]

Fix the issue 356

We should make the expire days longer, the default expires days is 30, we change it to 3650.

[Ayush-Singhal28]

@kinderyj Could you please confirm this solution working on Kubernetes. Reason being same solution I was using but when I describe crt. It is still 30days. In order to check
kubectl get secret webhook-server-cert -n flink-operator-system -o yaml
Copy the tls.crt content and decode it
echo "---crt----" | base64 -d > webhook.crt
When you open this webhook,crt file. You will see expiry still 30days. Though your command is correct

[kinderyj]

@kinderyj Could you please confirm this solution working on Kubernetes. Reason being same solution I was using but when I describe crt. It is still 30days. In order to check
kubectl get secret webhook-server-cert -n flink-operator-system -o yaml
Copy the tls.crt content and decode it
echo "---crt----" | base64 -d > webhook.crt
When you open this webhook,crt file. You will see expiry still 30days. Though your command is correct

My test steps:

0. In Nov 18, changed the args -days to 1 and installed the flink-operator by helm chart.
   openssl x509 -days 1 -req -CA ca.crt -CAkey ca.key -CAcreateserial -out ${tmpdir}/server-cert.pem

1. kubectl get secret webhook-server-cert -n flink-operator-system -o yaml

2. Copy the tls.crt content and base64 to a new file, such as webhook.crt
   echo "tls.crt content......" | base64 -d > webhook.crt

3. decode:
   openssl x509 -noout -text -in webhook.crt

The result is as below

You can see the Not Before is Nov 18 and Not After is Nov 19, only 1 day, it seems work.

Certificate:
    Data:
        Version: 1 (0x0)
        Serial Number:
           xxxxx
    Signature Algorithm: xxxxxx
        Issuer: CN=Admission Controller Webhook CA
        Validity
            Not Before: Nov 18 08:41:18 2020 GMT
            Not After : Nov 19 08:41:18 2020 GMT
        Subject: CN=flink-operator-webhook-service.flink-operator-system.svc
        ......

4. In Nov 19, I tried to create flink operator and reproduced the issue 355.

5. Changed the args -days to 3650 and repeat the steps above, the Validity is as below, it's 10 years.

Certificate:
    Data:
        Version: 1 (0x0)
        Serial Number:
           xxxxx
    Signature Algorithm: xxx
        Issuer: CN=Admission Controller Webhook CA
        Validity
            Not Before: Nov 24 14:20:29 2020 GMT
            Not After : Nov 22 14:20:29 2030 GMT
      ........

[functicons]

Thanks for the PR!

[functicons]

/gcbrun