add toplevel ssl opts

[reutsharabani]

Adds common ssl configuration as toplevel params

[hoplers]

Personally I think that adding top-level configuration properties for Ketu is redundant, and that top-level configuration should be kept only for mandatory configuration (e.g brokers, group-id).
Having properties as top-level requires us to copy the configurations from Kafka clients, sometimes giving them different names - without any significant added value, but with the pain of needing to maintain this parity (and also sometimes having configurations both in top-level and in :internal-config).
WDYT?

[reutsharabani]

Personally I think that adding top-level configuration properties for Ketu is redundant, and that top-level configuration should be kept only for mandatory configuration (e.g brokers, group-id). Having properties as top-level requires us to copy the configurations from Kafka clients, sometimes giving them different names - without any significant added value, but with the pain of needing to maintain this parity (and also sometimes having configurations both in top-level and in :internal-config). WDYT?

I tend to agree for now because no one should actually be using it manually. The best option is to generate this config using our internal libraries so the opportunity for error is small.

If people will start using SSL manually using internal-config it will have value in the sense of writing code (completion), readability, and also somewhat by validating the values conform to the spec.