naming

src/main/java/dev/ai4j/openai4j/OpenAiClient.java

@@ -74,7 +74,7 @@ public abstract static class Builder<T extends OpenAiClient, B extends Builder<T
  public LogLevel logLevel = DEBUG;
  public boolean logStreamingResponses;
  public Path persistTo;
- public Map<String, String> additionalHeaders;
+ public Map<String, String> customHeaders;
 
  public abstract T build();