Add an exception for the R66 TLS certificate

Our sister product Waarp-R66 comes packaged with a certificate to make R66-TLS transfers. While it was originally only meant to be used as an example or for testing, because changing certificates in Waarp-R66 is very complicated, this certificate is now used in production by several of our clients. However, this certificate is no longer valid, and is thus (rightly) rejected by the gateway when a Waarp-R66 partner presents it. This makes it impossible to do transfers between Waarp-R66 and the Gateway using TLS.

The only simple way to fix this issue without compromising the Gateway's security too much is to add an exception for this specific certificate to skip its validation. By default, this behavior will be turned off (for security reasons), and can be activated with an environment variable. Once this certificate is no longer in circulation, we will remove this exception.