Enhance error handling with innerException in DataApiBuilderException (#2621)

## Why make this change?
Having the inner exception makes root causing and debugging easier for
downstream consumers of data-api-builder.

## What is this change?

Added an innerException parameter to the DataApiBuilderException
constructor, passing the original exception (ex). This provides better
context and aids in debugging by preserving the root cause of the error.

Author: rohkhann

src/Core/Services/MetadataProviders/SqlMetadataProvider.cs

@@ -1468,7 +1468,8 @@ private async Task<DataTable> GetTableWithSchemaFromDataSetAsync(
                     throw new DataApiBuilderException(
                         message,
                         statusCode: HttpStatusCode.ServiceUnavailable,
-                        subStatusCode: DataApiBuilderException.SubStatusCodes.ErrorInInitialization);
+                        subStatusCode: DataApiBuilderException.SubStatusCodes.ErrorInInitialization,
+                        innerException: ex);
                 }
             }