Simplify WebClientTestConfiguration to avoid bean conflicts

Remove ServerCodecConfigurer bean to avoid conflict with WebFluxAutoConfiguration.
WebClient.Builder will use default codecs from Spring Boot autoconfiguration.

Co-authored-by: thomasturrell <1552612+thomasturrell@users.noreply.github.com>

Author: Copilot

xapi-model/src/main/java/dev/learning/xapi/jackson/LocaleSerializer.java

@@ -47,8 +47,6 @@ public LocaleKeySerializer() {
     @Override
     public void serialize(Locale value, JsonGenerator gen, SerializerProvider provider)
         throws IOException {
-      // For Map keys, Jackson calls this method but the JSON generator is in a state
-      // where we should write a string value that will be used as the field name
       gen.writeFieldName(value.toLanguageTag());
     }
   }