MQTT SSL: Support for self-signed server certificates

[blubiz-code]

httpshostnameverificationenabled was not working in my case
i got the error: PKIX path validation failed

Feature description

Solution

The solution on plugin side would be an optional parameter to provide the servers certificate files.

Solution Example
E.g. in Node-Red you can upload an server certificate:

Implementation hint
I think this stackoverflow posts are talking about an solution for the problem:

As described here https://stackoverflow.com/questions/65108693/eclipse-paho-mqtt-client-in-java-using-tls

"supply a custom SSLSocketFactory"

see https://github.com/iakko/mqtt-paho-tls-example for an implementation