feat(zhipuai): Add usage field to ChatCompletionChunk and update tests

- Add `usage` field to `ChatCompletionChunk`
- Update integration and unit tests to use free model (`glm-4-flash`) and verify `usage` field

Fixed #4609

Signed-off-by: YunKui Lu <[email protected]>

Author: YunKuiLu

models/spring-ai-zhipuai/src/main/java/org/springframework/ai/zhipuai/api/ZhiPuAiApi.java

@@ -284,7 +284,7 @@ public Flux<ChatCompletionChunk> chatCompletionStream(ChatCompletionRequest chat
 			})
 			.concatMapIterable(window -> {
 				Mono<ChatCompletionChunk> monoChunk = window
-					.reduce(new ChatCompletionChunk(null, null, null, null, null, null), this.chunkMerger::merge);
+					.reduce(new ChatCompletionChunk(null, null, null, null, null, null, null), this.chunkMerger::merge);
 				return List.of(monoChunk);
 			})
 			.flatMap(mono -> mono);
@@ -1110,7 +1110,8 @@ public record ChatCompletionChunk(// @formatter:off
 			@JsonProperty("created") Long created,
 			@JsonProperty("model") String model,
 			@JsonProperty("system_fingerprint") String systemFingerprint,
-			@JsonProperty("object") String object) { // @formatter:on
+			@JsonProperty("object") String object,
+		    @JsonProperty("usage") Usage usage) { // @formatter:on
 
 		/**
 		 * Chat completion choice.

models/spring-ai-zhipuai/src/main/java/org/springframework/ai/zhipuai/api/ZhiPuAiStreamFunctionCallingHelper.java

@@ -58,13 +58,14 @@ public ChatCompletionChunk merge(ChatCompletionChunk previous, ChatCompletionChu
 		String systemFingerprint = (current.systemFingerprint() != null ? current.systemFingerprint()
 				: previous.systemFingerprint());
 		String object = (current.object() != null ? current.object() : previous.object());
+		ZhiPuAiApi.Usage usage = (current.usage() != null ? current.usage() : previous.usage());
 
 		ChunkChoice previousChoice0 = (CollectionUtils.isEmpty(previous.choices()) ? null : previous.choices().get(0));
 		ChunkChoice currentChoice0 = (CollectionUtils.isEmpty(current.choices()) ? null : current.choices().get(0));
 
 		ChunkChoice choice = merge(previousChoice0, currentChoice0);
 		List<ChunkChoice> chunkChoices = choice == null ? List.of() : List.of(choice);
-		return new ChatCompletionChunk(id, chunkChoices, created, model, systemFingerprint, object);
+		return new ChatCompletionChunk(id, chunkChoices, created, model, systemFingerprint, object, usage);
 	}
 
 	private ChunkChoice merge(ChunkChoice previous, ChunkChoice current) {

models/spring-ai-zhipuai/src/test/java/org/springframework/ai/zhipuai/api/ZhiPuAiApiIT.java

@@ -57,21 +57,24 @@ void chatCompletionEntity() {
 	void chatCompletionEntityWithMoreParams() {
 		ChatCompletionMessage chatCompletionMessage = new ChatCompletionMessage("Hello world", Role.USER);
 		ResponseEntity<ChatCompletion> response = this.zhiPuAiApi
-			.chatCompletionEntity(new ChatCompletionRequest(List.of(chatCompletionMessage), "glm-3-turbo", 1024, null,
+			.chatCompletionEntity(new ChatCompletionRequest(List.of(chatCompletionMessage), "glm-4-flash", 1024, null,
 					false, 0.95, 0.7, null, null, null, "test_request_id", false, null, null));
 
 		assertThat(response).isNotNull();
 		assertThat(response.getBody()).isNotNull();
+		assertThat(response.getBody().usage()).isNotNull();
 	}
 
 	@Test
 	void chatCompletionStream() {
 		ChatCompletionMessage chatCompletionMessage = new ChatCompletionMessage("Hello world", Role.USER);
 		Flux<ChatCompletionChunk> response = this.zhiPuAiApi
-			.chatCompletionStream(new ChatCompletionRequest(List.of(chatCompletionMessage), "glm-3-turbo", 0.7, true));
+			.chatCompletionStream(new ChatCompletionRequest(List.of(chatCompletionMessage), "glm-4-flash", 0.7, true));
 
 		assertThat(response).isNotNull();
-		assertThat(response.collectList().block()).isNotNull();
+		List<ChatCompletionChunk> chunks = response.collectList().block();
+		assertThat(chunks).isNotNull();
+		assertThat(chunks.get(chunks.size() - 1).usage()).isNotNull();
 	}
 
 	@Test

models/spring-ai-zhipuai/src/test/java/org/springframework/ai/zhipuai/api/ZhiPuAiRetryTests.java

@@ -133,7 +133,7 @@ public void zhiPuAiChatStreamTransientError() {
 		var choice = new ChatCompletionChunk.ChunkChoice(ChatCompletionFinishReason.STOP, 0,
 				new ChatCompletionMessage("Response", Role.ASSISTANT), null);
 		ChatCompletionChunk expectedChatCompletion = new ChatCompletionChunk("id", List.of(choice), 666L, "model", null,
-				null);
+				null, null);
 
 		given(this.zhiPuAiApi.chatCompletionStream(isA(ChatCompletionRequest.class)))
 			.willThrow(new TransientAiException("Transient Error 1"))