[IMPROVEMENT] Generate a unique CA Serial Number

[aborroy]

Currently the serial number for CA certificate is set to a fixed value (1000) every time:

https://github.com/Alfresco/alfresco-ssl-generator/blob/master/ssl-tool/run.sh#L183

Improvement

When creating the CA, a unique serial number should be generated.

The code needs to be adapted to use openssl ca -create_serial feature.

Reference: https://github.com/ecm4u/alf-genssl/blob/main/alf-genssl.sh#L76