Add external tables (#255)

Author: ishmum123

dumper/app/src/main/java/com/google/edwmigration/dumper/application/dumper/connector/snowflake/SnowflakeMetadataConnector.java

@@ -271,6 +271,12 @@ public void addTasksTo(
           "SHOW WAREHOUSES",
           new TaskVariant(WarehousesFormat.AU_ZIP_ENTRY_NAME, AU));
 
+      addSingleSqlTask(
+          out,
+          ExternalTablesFormat.Header.class,
+          "SHOW EXTERNAL TABLES",
+          new TaskVariant(ExternalTablesFormat.AU_ZIP_ENTRY_NAME, AU));
+
       addSingleSqlTask(
           out,
           FunctionsViewFormat.Header.class,

dumper/lib-dumper-spi/src/main/java/com/google/edwmigration/dumper/plugin/lib/dumper/spi/SnowflakeMetadataDumpFormat.java

@@ -192,4 +192,31 @@ enum Header {
       ScalingPolicy,
     }
   }
+
+  interface ExternalTablesFormat {
+
+    String AU_ZIP_ENTRY_NAME = "external_tables.csv";
+
+    enum Header {
+      CreatedOn,
+      Name,
+      DatabaseName,
+      SchemaName,
+      Invalid,
+      InvalidReason,
+      Owner,
+      Comment,
+      Stage,
+      Location,
+      FileFormatName,
+      FileFormatType,
+      Cloud,
+      Region,
+      NotificationChannel,
+      LastRefreshDetails,
+      TableFormat,
+      LastRefreshedOn,
+      OwnerRoleType,
+    }
+  }
 }