[ES-1006739] Minor change in connection to get UC Volume client (#383)

* Minor change in connection to get UC Volume client

* Minor change

Author: gopalldb

src/main/java/com/databricks/jdbc/core/DatabricksConnection.java

@@ -2,6 +2,8 @@
 
 import com.databricks.client.jdbc.Driver;
 import com.databricks.jdbc.client.DatabricksClient;
+import com.databricks.jdbc.client.IDatabricksUCVolumeClient;
+import com.databricks.jdbc.client.impl.sdk.DatabricksUCVolumeClient;
 import com.databricks.jdbc.commons.LogLevel;
 import com.databricks.jdbc.commons.util.LoggingUtil;
 import com.databricks.jdbc.commons.util.ValidationUtil;
@@ -23,6 +25,8 @@ public class DatabricksConnection implements IDatabricksConnection, Connection {
   private final Set<IDatabricksStatement> statementSet = ConcurrentHashMap.newKeySet();
   private SQLWarning warnings = null;
 
+  private IDatabricksUCVolumeClient ucVolumeClient = null;
+
   /**
    * Creates an instance of Databricks connection for given connection context.
    *
@@ -563,6 +567,14 @@ public Connection getConnection() {
     return this;
   }
 
+  @Override
+  public IDatabricksUCVolumeClient getUCVolumeClient() {
+    if (ucVolumeClient == null) {
+      ucVolumeClient = new DatabricksUCVolumeClient(this);
+    }
+    return ucVolumeClient;
+  }
+
   private void throwExceptionIfConnectionIsClosed() throws SQLException {
     if (this.isClosed()) {
       throw new DatabricksSQLException("Connection closed!");

src/main/java/com/databricks/jdbc/core/IDatabricksConnection.java

@@ -1,5 +1,6 @@
 package com.databricks.jdbc.core;
 
+import com.databricks.jdbc.client.IDatabricksUCVolumeClient;
 import java.sql.Connection;
 
 /** Interface providing Databricks specific Connection APIs. */
@@ -17,4 +18,7 @@ public interface IDatabricksConnection {
 
   /** Returns the corresponding sql connection object */
   Connection getConnection();
+
+  /** Returns a UC Volume client instance */
+  IDatabricksUCVolumeClient getUCVolumeClient();
 }

src/test/java/com/databricks/jdbc/core/DatabricksConnectionTest.java

@@ -146,6 +146,14 @@ public void testConfInConnection() throws SQLException {
     assertEquals(connection.getSession().getSessionConfigs(), lowercaseSessionConfigs);
   }
 
+  @Test
+  public void testGetUCVolumeClient() throws SQLException {
+    IDatabricksConnectionContext connectionContext =
+        DatabricksConnectionContext.parse(SESSION_CONF_JDBC_URL, new Properties());
+    DatabricksConnection connection = new DatabricksConnection(connectionContext, databricksClient);
+    assertNotNull(connection.getUCVolumeClient());
+  }
+
   @Test
   public void testStatement() throws DatabricksSQLException {
     when(databricksClient.createSession(