Fix compilation

Signed-off-by: Sicheng Song <sicheng.song@outlook.com>

Author: b4sjoo

common/src/main/java/org/opensearch/ml/common/connector/HttpConnector.java

@@ -11,6 +11,7 @@
 import lombok.extern.log4j.Log4j2;
 import org.apache.commons.text.StringSubstitutor;
 import org.opensearch.common.io.stream.BytesStreamOutput;
+import org.opensearch.commons.authuser.User;
 import org.opensearch.core.common.io.stream.StreamInput;
 import org.opensearch.core.common.io.stream.StreamOutput;
 import org.opensearch.core.xcontent.XContentBuilder;