feat(Converter): 支持动态字段映射与解析

- 在 MilvusConverter 中添加对动态字段的处理逻辑(目的为了query()无outputFields能获取到$meta)
- 在 SearchRespConverter 中增加对 $meta 字段的解析

milvus-plus-core/src/main/java/org/dromara/milvus/plus/converter/MilvusConverter.java

@@ -94,6 +94,9 @@ public class MilvusConverter {
         for (Field field : fields) {
             MilvusField fieldAnnotation = field.getAnnotation(MilvusField.class);
             if (Objects.isNull(fieldAnnotation)) {
+                if (collectionAnnotation.enableDynamicField()) {
+                    propertyCache.functionToPropertyMap.put("$meta", "$meta");
+                }
                 continue;
             }
             // 处理字段名，优先使用注解中的字段名，若无则用反射获取的字段名

milvus-plus-core/src/main/java/org/dromara/milvus/plus/converter/SearchRespConverter.java

@@ -41,7 +41,13 @@ public class SearchRespConverter {
                     Map<String, Object> entityMap = new HashMap<>();
                     for (Map.Entry<String, Object> entry : searchResult.getEntity().entrySet()) {
                         String key = propertyCache.findKeyByValue(entry.getKey());
-                        if(key!=null){
+                        if (conversionCache.getMilvusEntity().getEnableDynamicField()
+                                && "$meta".equals(entry.getKey())) {
+                            if (entry.getValue() == null) {
+                                continue;
+                            }
+                            entityMap.putAll(GsonUtil.fromJsonToMap(entry.getValue().toString()));
+                        } else if(key!=null){
                             Object value = entry.getValue();
                             entityMap.put(key,value);
                         }