Generate dummy VPN certificate for testing
The Yunohost CI cannot run the renew script, as the openvpn client is not installed in the test environment.
The script is reading credentials from /etc/openvpn/keys/credentials, and the public certificate from /etc/openvpn/keys/user.crt. Then, it is calling the renew_cert python script [1], which will just check the expiration date of the certificate. It will do complex stuff only when the certificate must be renewed.