Add support for custom JSON payload in ChatCompletionContentPart

[FanYaning]

Fix: #700

        ChatCompletionContentPart textPart = ChatCompletionContentPart.ofText(ChatCompletionContentPartText.builder()
                .text(promptMessage)
                .build());

        String type = visionMessage.startsWith("data:image/") ? "image_url" : "video_url";
        Map<String, JsonValue> part = Map.of(
                "type", JsonValue.from(type),
                type, JsonValue.from(Map.of("url", visionMessage)));

        ChatCompletionContentPart visionPart = ChatCompletionContentPart.ofJson(JsonValue.from(part));

        ChatCompletionCreateParams createParams = ChatCompletionCreateParams.builder()
                .addUserMessageOfArrayOfContentParts(List.of(visionPart, textPart))
                .model(config.getModelV())
                .temperature(config.getTemperatureV())
                .putAllAdditionalBodyProperties(customProps)
                .build();

[Guokeeng]

我也遇到这个问题了，很需要这个提交，怎么4个月了都没人复审呢？？？

[dpiet-oai]

Thanks for the contribution. The request in #700 is already supported through ChatCompletionUserMessageParam.builder().content(JsonValue.from(parts)).build(). We verified that serialization preserves the custom video_url object and adjacent text part. We're closing this PR because no new factory is needed for that use case. This verification covers request serialization only, not the provider's video processing.