Support `kafka` AsyncAPI validation cases

[jfallows]

Describe the desired outcome from the user's perspective As an API consumer, I want to define OpenAPI validation behavior of zilla using the corresponding AsyncAPI specification document for the HTTP, MQTT or Kafka API.

Acceptance criteria

• kafka topic name parameter validation

Additional context Review any remaining validation syntax in AsyncAPI for enforcement via zilla model validation. See Kafka streetlights AsyncAPI spec as an example.

Tasks

• [ ] validate kafka topic parameter name matches enum
• [ ] validate kafka topic parameter name matches json pointer location within message header
• [ ] validate kafka topic parameter name matches json pointer location within message payload

Note: Kafka streetlights AsyncAPI spec defines {streetlightId} in channel addresses but does not require enum or json pointer validation.