Refactor configuration parsing

[hariso]

The connector's configuration consists of a number of parameters of different types and with different validations. Currently, we're parsing fields one by one. If the configuration continues growing, we should look into a more generic way to parse configurations, to keep maintainable code.

Another thing to consider here are parameters for explicitly enabing/disabling TLS. Currently, TLS is considered enabled if any TLS setting is present.