This makes the generated certificates compatible with security
level 2, which is apparently the default on Ubuntu 20.04.
Unfortunately this does not fix all tests, because some are using
pre-generated certificates.
The idea is to create an easy way to provide a certificate that never
expires. In order to make it cross-platform, PHP is used rather than
openssl CLI app. Using openssl to generate certificates for tests that
test openssl might be not the best idea but pros seem to outweight cons
that this "recursice dependency" adds