fix: Update spec_version checks

Signed-off-by: Daniel Azuma <dazuma@gmail.com>

Author: dazuma

lib/cloud_events/kafka_binding.rb

@@ -209,7 +209,7 @@ def encode_event(event, structured_format: false, key_mapper: :NOT_SET, **format
       if event.is_a?(Event::Opaque)
         return encode_opaque_event(event)
       end
-      unless event.spec_version.start_with?("1")
+      unless event.respond_to?(:spec_version) && event.spec_version.start_with?("1.")
         raise(SpecVersionError, "Unrecognized specversion: #{event.spec_version}")
       end
       if structured_format
@@ -286,7 +286,7 @@ def decode_structured_content(message, content_type, allow_opaque, **format_args
                                             **format_args)
       if result
         event = result[:event]
-        if event && !event.spec_version.start_with?("1")
+        if event && !(event.respond_to?(:spec_version) && event.spec_version.start_with?("1."))
           raise(SpecVersionError, "Unrecognized specversion: #{event.spec_version}")
         end
         return event