Refactor OpenAiUnifiedChatCompletionRequestEntity to remove unused fields and streamline constructor

Author: Jan-Kazlouski-elastic

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/openai/request/OpenAiUnifiedChatCompletionRequestEntity.java

@@ -21,15 +21,10 @@
 public class OpenAiUnifiedChatCompletionRequestEntity implements ToXContentObject {
 
     public static final String USER_FIELD = "user";
-    private static final String MODEL_FIELD = "model";
-    private static final String MAX_COMPLETION_TOKENS_FIELD = "max_completion_tokens";
-
-    private final UnifiedChatInput unifiedChatInput;
     private final OpenAiChatCompletionModel model;
     private final UnifiedChatCompletionRequestEntity unifiedRequestEntity;
 
     public OpenAiUnifiedChatCompletionRequestEntity(UnifiedChatInput unifiedChatInput, OpenAiChatCompletionModel model) {
-        this.unifiedChatInput = Objects.requireNonNull(unifiedChatInput);
         this.unifiedRequestEntity = new UnifiedChatCompletionRequestEntity(unifiedChatInput);
         this.model = Objects.requireNonNull(model);
     }