Added support for stream_options in chat completions

Fixes: TheoKanning#502

api/src/main/java/com/theokanning/openai/completion/chat/ChatCompletionChunk.java

@@ -1,4 +1,5 @@
 package com.theokanning.openai.completion.chat;
+import com.theokanning.openai.Usage;
 import lombok.Data;
 
 import java.util.List;
@@ -32,4 +33,9 @@ public class ChatCompletionChunk {
      * A list of all generated completions.
      */
     List<ChatCompletionChoice> choices;
-}
+
+    /**
+     * The API usage for this request
+     */
+    Usage usage;
+}

api/src/main/java/com/theokanning/openai/completion/chat/ChatCompletionRequest.java

@@ -54,6 +54,13 @@ public class ChatCompletionRequest {
      */
     Boolean stream;
 
+    /**
+     * Options for streaming response. Only set this when you set stream: true
+     * <a href="https://platform.openai.com/docs/api-reference/chat/create#chat-create-stream_options">OpenAI Docs</a>
+     */
+    @JsonProperty("stream_options")
+    StreamOptions streamOptions;
+
     /**
      * Up to 4 sequences where the API will stop generating further tokens.
      */

api/src/main/java/com/theokanning/openai/completion/chat/StreamOptions.java

@@ -0,0 +1,25 @@
+package com.theokanning.openai.completion.chat;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * <p>Options for streaming response. Only set this when you set stream: true</p>
+ * see <a href="https://platform.openai.com/docs/api-reference/chat/create#chat-create-stream_options">OpenAi documentation</a>
+ */
+@Data
+@NoArgsConstructor(force = true)
+@AllArgsConstructor
+public class StreamOptions {
+
+	/**
+	 * If set, an additional chunk will be streamed before the data: [DONE] message.
+	 * The usage field on this chunk shows the token usage statistics for the entire request, and the choices field will always be an empty array.
+	 * All other chunks will also include a usage field, but with a null value.
+	 */
+	@JsonProperty("include_usage")
+	Boolean includeUsage;
+
+}

service/src/test/java/com/theokanning/openai/service/ChatCompletionTest.java

@@ -84,6 +84,31 @@ void streamChatCompletion() {
         assertNotNull(chunks.get(0).getChoices().get(0));
     }
 
+    @Test
+    void streamChatCompletionWithStreamOptions() {
+        final List<ChatMessage> messages = new ArrayList<>();
+        final ChatMessage systemMessage = new ChatMessage(ChatMessageRole.SYSTEM.value(), "You are a dog and will speak as such.");
+        messages.add(systemMessage);
+
+        ChatCompletionRequest chatCompletionRequest = ChatCompletionRequest
+                .builder()
+                .model("gpt-3.5-turbo")
+                .messages(messages)
+                .n(1)
+                .maxTokens(50)
+                .logitBias(new HashMap<>())
+                .stream(true)
+                .streamOptions(new StreamOptions(true))
+                .build();
+
+        List<ChatCompletionChunk> chunks = new ArrayList<>();
+        service.streamChatCompletion(chatCompletionRequest).blockingForEach(chunks::add);
+        assertTrue(chunks.size() > 0);
+        assertNotNull(chunks.get(0).getChoices().get(0));
+        chunks.stream().limit(chunks.size() - 1).forEach(chunk -> assertNull(chunk.getUsage()));
+        assertNotNull(chunks.get(chunks.size()-1).getUsage());
+    }
+
     @Test
     void createChatCompletionWithFunctions() {
         final List<ChatFunction> functions = Collections.singletonList(ChatFunction.builder()