Allow specifying attribute configuration using a "connection string"

[gliljas]

This is more a POC than a PR. It gives a somewhat weird but also convenient way to handle the issue mentioned in #161. I've experimented with a few ways, but attributes are very special in what you can do, so this turned out to be an OK solution.

The attribute mentioned in the issue could be written as:

[KafkaTrigger(@"%Broker%",
              @"%TopicName%",
              @"Protocol = %Protocol%;
                AuthenticationMode = %AuthenticationMode%",  
              SslCaLocation = @"%CaFile%",
              Username = @"%Username%",
              Password = @"%Password%",
              ConsumerGroup = "%ConsumerGroup%" )] KafkaEventData<byte[]>[] events,

...and that special constructor would only have to be used in these scenarios.

[gliljas]

Maybe it should be named as "connectionstring", and be the only argument to the function.

[TsuyoshiUshio]

hi @gliljas
Thank you for the PoC. It looks cool. However, we need to consider if it works with Java/Python and other languages. It is unclear for me, so need to investigation.