Improve naming of the SSL options

[tinaselenge]

Based on the recent discussion, naming for some of the SSL properties were confusing as they mix "keystore" terminology with PEM certificate/key terminology. This PR attempts to make them clearer, with more consistent terminology.

In the future, if we need to support more formats (not sure if we will ever need to do), we could add:

• http.ssl.format=PEM | PKCS12 | JKS (default: PEM)
• http.ssl.keystore.password (when needed for pkcs12/jks)

[scholzj]

I'm not entirely sure why did you changed location to path. I'm pretty flexible and can use both. But given Kafka uses location, I wonder if that was better? (that said, the option names anyway differ, so maybe we don't care?)

[scholzj]

So, if we call this http.ssl.certificate / http.ssl.certificate.path ... how would we call the trusted certificates if we one day add support for mTLS authentication?

[ppatierno]

@tinaselenge I had a view and my thoughts are:

• I would stick with location and not using path. Users using the HTTP bridge are more familiar with Apache Kafka naming than internal stuff (the Java methods using Path).
• Also I would take keystore as well.

Tbh at this point I am not sure why we are making these changes here.

[katheris]

I think the confusion here is that the settings are similar to the Kafka settings, but actually the way the user provides them is different from Kafka. So for example in Kafka you can provide these configurations for files:
ssl.keystore.type (PEM or JKS or PKCS12)
ssl.keystore.location
ssl.keystore.password
ssl.key.password
ssl.truststore.type (PEM or JKS or PKCS12)
ssl.truststore.location
ssl.truststore.password

Where ssl.keystore.location contains both the private key and the public certificate. Whereas for Bridge we have the key and certificate as separate files:
http.ssl.keystore.certificate.location
http.ssl.keystore.key.location

So given the starting point I'm not sure what can be changed to make it less confusing