refactor(azure): replace LinkedHashMap with HashMap in parseMetadataToMutable

We don’t rely on insertion order for metadata, so a regular HashMap is sufficient.
This change addresses reviewer feedback while still ensuring the returned map is
always mutable by creating a defensive copy or returning an empty instance.

Relates to #4117

Signed-off-by: Jinwoo Lee <[email protected]>

Author: jinlee1703

vector-stores/spring-ai-azure-store/src/main/java/org/springframework/ai/vectorstore/azure/AzureVectorStore.java

@@ -18,7 +18,7 @@
 
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.LinkedHashMap;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -325,16 +325,16 @@ public <T> Optional<T> getNativeClient() {
 
 	static Map<String, Object> parseMetadataToMutable(@Nullable String metadataJson) {
 		if (!StringUtils.hasText(metadataJson)) {
-			return new LinkedHashMap<>();
+			return new HashMap<>();
 		}
 		try {
 			Map<String, Object> parsed = JSONObject.parseObject(metadataJson, new TypeReference<Map<String, Object>>() {
 			});
-			return (parsed == null) ? new LinkedHashMap<>() : new LinkedHashMap<>(parsed);
+			return (parsed == null) ? new HashMap<>() : new HashMap<>(parsed);
 		}
 		catch (Exception ex) {
 			logger.warn("Failed to parse metadata JSON. Using empty metadata. json={}", metadataJson, ex);
-			return new LinkedHashMap<>();
+			return new HashMap<>();
 		}
 	}