Fix so generic data source returns typed information

Author: Ulimo

src/FlowtideDotNet.Core/Sources/Generic/Internal/GenericTableProvider.cs

@@ -10,7 +10,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+using FlowtideDotNet.Core.ColumnStore.ObjectConverter;
 using FlowtideDotNet.Substrait.Sql;
+using FlowtideDotNet.Substrait.Type;
 using System.Diagnostics.CodeAnalysis;
 
 namespace FlowtideDotNet.Core.Sources.Generic.Internal
@@ -21,18 +23,14 @@ internal class GenericTableProvider<T> : ITableProvider
 
         public GenericTableProvider(string name)
         {
-            var properties = typeof(T).GetProperties();
-            var columnNames = properties.Select(x =>
+            var schema = BatchConverter.GetBatchConverter(typeof(T)).GetSchema();
+            schema.Names.Add("__key");
+            if (schema.Struct != null)
             {
-                return x.Name;
-            }).ToList();
-
-            columnNames.Add("__key");
-
-            _tableMetadata = new TableMetadata(name, new Substrait.Type.NamedStruct()
-            {
-                Names = columnNames
-            });
+                schema.Struct.Types.Add(new StringType());
+            }
+            
+            _tableMetadata = new TableMetadata(name, schema);
         }
 
         public bool TryGetTableInformation(IReadOnlyList<string> tableName, [NotNullWhen(true)] out TableMetadata? tableMetadata)