set registration metadata modifiedable

spring-cloud-starter-tencent-polaris-discovery/src/main/java/com/tencent/cloud/polaris/registry/PolarisRegistration.java

@@ -54,7 +54,7 @@ public class PolarisRegistration implements Registration {
 
 	private Map<String, String> metadata;
 
-	private final String host;
+	private String host;
 
 	public PolarisRegistration(
 			PolarisDiscoveryProperties polarisDiscoveryProperties,
@@ -78,6 +78,10 @@ public class PolarisRegistration implements Registration {
 		return host;
 	}
 
+	public void setHost(String host) {
+		this.host = host;
+	}
+
 	@Override
 	public int getPort() {
 		return polarisDiscoveryProperties.getPort();
@@ -108,7 +112,7 @@ public class PolarisRegistration implements Registration {
 
 			instanceMetadata.putAll(staticMetadataManager.getMergedStaticMetadata());
 
-			this.metadata = Collections.unmodifiableMap(instanceMetadata);
+			this.metadata = instanceMetadata;
 		}
 		return metadata;
 	}